fix: pdfrx doesn't react to open another document due to fixed sourceName and viewerKey.

integration_test/export_flow_test.dart

@@ -39,7 +39,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) =>
                 DocumentStateNotifier(service: ExportService())
-                  ..openPicked(pageCount: 3, bytes: pdfBytes),
+                  ..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -95,7 +95,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) =>
                 DocumentStateNotifier(service: ExportService())
-                  ..openPicked(pageCount: 3, bytes: pdfBytes),
+                  ..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -164,7 +164,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) => DocumentStateNotifier(
               service: ExportService(enableRaster: false),
-            )..openPicked(pageCount: 3, bytes: pdfBytes),
+            )..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -210,7 +210,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) => DocumentStateNotifier(
               service: ExportService(enableRaster: false),
-            )..openPicked(pageCount: 3, bytes: pdfBytes),
+            )..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -259,7 +259,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) => DocumentStateNotifier(
               service: ExportService(enableRaster: false),
-            )..openPicked(pageCount: 3, bytes: pdfBytes),
+            )..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -311,7 +311,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) =>
                 DocumentStateNotifier(service: ExportService())
-                  ..openPicked(pageCount: 3, bytes: pdfBytes),
+                  ..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -363,7 +363,7 @@ void main() {
             documentRepositoryProvider.overrideWith(
               (ref) =>
                   DocumentStateNotifier(service: ExportService())
-                    ..openPicked(pageCount: 3, bytes: pdfBytes),
+                    ..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
             ),
             pdfViewModelProvider.overrideWith(
               (ref) => PdfViewModel(ref, useMockViewer: false),

integration_test/pdf_view_test.dart

@@ -34,7 +34,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) =>
                 DocumentStateNotifier()
-                  ..openPicked(pageCount: 3, bytes: pdfBytes),
+                  ..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -62,14 +62,31 @@ void main() {
     final vm = container.read(pdfViewModelProvider);
     expect(vm.currentPage, 1);
 
-    container.read(pdfViewModelProvider.notifier).jumpToPage(2);
+    final controller = container.read(pdfViewModelProvider).controller;
-    await tester.pumpAndSettle();
+    // Wait until the underlying viewer controller reports ready.
-    await tester.pump(const Duration(milliseconds: 120));
+    final readyStart = DateTime.now();
-    expect(container.read(pdfViewModelProvider).currentPage, 2);
+    while (!controller.isReady) {
+      await tester.pump(const Duration(milliseconds: 40));
+      if (DateTime.now().difference(readyStart) > const Duration(seconds: 5)) {
+        fail('PdfViewerController never became ready');
+      }
+    }
+    Future<void> goAndAwait(int target) async {
+      controller.goToPage(pageNumber: target);
+      final start = DateTime.now();
+      while (container.read(pdfViewModelProvider).currentPage != target) {
+        await tester.pump(const Duration(milliseconds: 40));
+        if (DateTime.now().difference(start) > const Duration(seconds: 3)) {
+          fail(
+            'Timeout waiting to reach page $target (current=${container.read(pdfViewModelProvider).currentPage})',
+          );
+        }
+      }
+    }
 
-    container.read(pdfViewModelProvider.notifier).jumpToPage(3);
+    await goAndAwait(2);
-    await tester.pumpAndSettle();
+    expect(container.read(pdfViewModelProvider).currentPage, 2);
-    await tester.pump(const Duration(milliseconds: 120));
+    await goAndAwait(3);
     expect(container.read(pdfViewModelProvider).currentPage, 3);
   });
 
@@ -88,7 +105,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) =>
                 DocumentStateNotifier()
-                  ..openPicked(pageCount: 3, bytes: pdfBytes),
+                  ..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -142,7 +159,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) =>
                 DocumentStateNotifier()
-                  ..openPicked(pageCount: 3, bytes: pdfBytes),
+                  ..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -229,7 +246,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) =>
                 DocumentStateNotifier()
-                  ..openPicked(pageCount: 3, bytes: pdfBytes),
+                  ..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -295,7 +312,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) =>
                 DocumentStateNotifier()
-                  ..openPicked(pageCount: 3, bytes: pdfBytes),
+                  ..openPickedWithPageCount(pageCount: 3, bytes: pdfBytes),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: false),
@@ -339,4 +356,113 @@ void main() {
     await tester.pumpAndSettle();
     expect(container.read(pdfViewModelProvider).currentPage, 3);
   });
+
+  testWidgets('PDF View: reopen another PDF via toolbar picker updates viewer', (
+    tester,
+  ) async {
+    final initialBytes =
+        await File('integration_test/data/sample-local-pdf.pdf').readAsBytes();
+    // 3 pages
+    final newBytes =
+        await File(
+          'integration_test/data/PPFZ-Local-Purchase-Form.pdf',
+        ).readAsBytes();
+    // 10 pages
+    SharedPreferences.setMockInitialValues({});
+    final prefs = await SharedPreferences.getInstance();
+
+    // We'll override onPickPdf to simulate opening a new file with a different page count
+    // TODO: Replace PPFZ-Local-Purchase-Form.pdf with a 10-page PDF to test page count change
+    late ProviderContainer container; // capture to use inside callback
+    Future<void> simulatePick() async {
+      container
+          .read(documentRepositoryProvider.notifier)
+          .openPicked(bytes: newBytes);
+      // Reset the current page explicitly to 1 as openPicked establishes new doc
+      container.read(pdfViewModelProvider.notifier).jumpToPage(1);
+    }
+
+    int? lastDocPageCount; // capture page count from callback
+    await tester.pumpWidget(
+      ProviderScope(
+        overrides: [
+          preferencesRepositoryProvider.overrideWith(
+            (ref) => PreferencesStateNotifier(prefs),
+          ),
+          documentRepositoryProvider.overrideWith(
+            (ref) =>
+                DocumentStateNotifier()
+                  ..openPickedWithPageCount(pageCount: 3, bytes: initialBytes),
+          ),
+          pdfViewModelProvider.overrideWith(
+            (ref) => PdfViewModel(ref, useMockViewer: false),
+          ),
+        ],
+        child: Builder(
+          builder: (context) {
+            container = ProviderScope.containerOf(context);
+            return MaterialApp(
+              localizationsDelegates: AppLocalizations.localizationsDelegates,
+              supportedLocales: AppLocalizations.supportedLocales,
+              locale: const Locale('en'),
+              home: PdfSignatureHomePage(
+                onPickPdf: simulatePick,
+                onClosePdf: () {},
+                currentFile: XFile('initial.pdf'),
+                // The only reliable way to detect the new document load correctly
+                onDocumentChanged: (doc) {
+                  if (doc != null) {
+                    lastDocPageCount = doc.pages.length;
+                  }
+                },
+              ),
+            );
+          },
+        ),
+      ),
+    );
+
+    await tester.pumpAndSettle();
+    // Verify initial state Page 1/3
+    expect(find.byKey(const Key('lbl_page_info')), findsOneWidget);
+    final initialLabel =
+        tester.widget<Text>(find.byKey(const Key('lbl_page_info'))).data;
+    expect(initialLabel, contains('/3'));
+
+    // Tap open picker button to simulate opening new PDF
+    await tester.tap(find.byKey(const Key('btn_open_pdf_picker')));
+    // Allow frame to process state changes from simulatePick
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 50));
+    await tester.pumpAndSettle();
+
+    // Wait for async page count detection to complete in repository
+    await tester.runAsync(() async {
+      final start = DateTime.now();
+      while (container.read(documentRepositoryProvider).pageCount != 10) {
+        await Future<void>.delayed(const Duration(milliseconds: 50));
+        await tester.pump();
+
+        if (DateTime.now().difference(start) > const Duration(seconds: 8)) {
+          final pageCount =
+              container.read(documentRepositoryProvider).pageCount;
+          fail(
+            'Timeout waiting for repository page count to update to 10 (current=$pageCount)',
+          );
+        }
+      }
+
+      // Wait for restoration mechanism to complete
+      await Future<void>.delayed(const Duration(milliseconds: 500));
+      await tester.pump();
+    });
+
+    final updatedLabel =
+        tester.widget<Text>(find.byKey(const Key('lbl_page_info'))).data;
+    expect(updatedLabel, contains('/10'));
+    // Verify that repository correctly analyzed PDF bytes and updated page count
+    expect(container.read(documentRepositoryProvider).pageCount, 10);
+    expect(lastDocPageCount, 10);
+    expect(container.read(pdfViewModelProvider).currentPage, 1);
+  });
 }

lib/data/repositories/document_repository.dart

@@ -4,6 +4,7 @@ import 'package:image/image.dart' as img;
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:pdf_signature/data/services/export_service.dart';
+import 'package:pdfrx/pdfrx.dart';
 
 import '../../domain/models/model.dart';
 
@@ -24,7 +25,61 @@ class DocumentStateNotifier extends StateNotifier<Document> {
     );
   }
 
-  void openPicked({required int pageCount, Uint8List? bytes}) {
+  void openPicked({Uint8List? bytes}) {
+    debugPrint(
+      '[DocumentRepository] openPicked called (bytes length: ${bytes?.length})',
+    );
+
+    // For real usage, determine page count from PDF bytes asynchronously
+    if (bytes != null) {
+      _openPickedAsync(bytes);
+    } else {
+      // Handle null bytes case
+      state = state.copyWith(
+        loaded: true,
+        pageCount: 1,
+        pickedPdfBytes: bytes,
+        placementsByPage: <int, List<SignaturePlacement>>{},
+      );
+    }
+  }
+
+  Future<void> _openPickedAsync(Uint8List bytes) async {
+    int pageCount = 1; // default fallback
+
+    try {
+      // Determine actual page count from PDF bytes
+      final doc = await PdfDocument.openData(bytes);
+      pageCount = doc.pages.length;
+      debugPrint('[DocumentRepository] PDF has $pageCount pages');
+    } catch (e) {
+      debugPrint('[DocumentRepository] Failed to read PDF page count: $e');
+      // Keep default pageCount = 1 on error
+    }
+
+    state = state.copyWith(
+      loaded: true,
+      pageCount: pageCount,
+      pickedPdfBytes: bytes,
+      placementsByPage: <int, List<SignaturePlacement>>{},
+    );
+
+    // Schedule delayed check to ensure our page count wasn't overridden by UI callbacks
+    Future.delayed(const Duration(milliseconds: 100), () {
+      if (state.loaded &&
+          state.pickedPdfBytes == bytes &&
+          state.pageCount != pageCount) {
+        state = state.copyWith(pageCount: pageCount);
+      }
+    });
+  }
+
+  // For tests that need to specify page count explicitly
+  @visibleForTesting
+  void openPickedWithPageCount({required int pageCount, Uint8List? bytes}) {
+    debugPrint(
+      '[DocumentRepository] openPickedWithPageCount called (pageCount=$pageCount)',
+    );
     state = state.copyWith(
       loaded: true,
       pageCount: pageCount,
@@ -39,6 +94,9 @@ class DocumentStateNotifier extends StateNotifier<Document> {
 
   void setPageCount(int count) {
     if (!state.loaded) return;
+    debugPrint(
+      '[DocumentRepository] setPageCount called: $count (current: ${state.pageCount})',
+    );
     state = state.copyWith(pageCount: count.clamp(1, 9999));
   }
 

lib/main.dart

@@ -1,12 +1,33 @@
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
+import 'package:pdfrx/pdfrx.dart';
+import 'package:path_provider/path_provider.dart';
+import 'dart:io';
 import 'package:pdf_signature/app.dart';
 export 'package:pdf_signature/app.dart';
 
-void main() {
+Future<void> _initPdfrxCache() async {
-  // Ensure Flutter bindings are initialized before platform channel usage
+  try {
+    // Only set once; guard for hot reload/tests
+    if (Pdfrx.getCacheDirectory == null) {
+      final dir = await getTemporaryDirectory();
+      final cacheDir = Directory('${dir.path}/pdfrx_cache');
+      if (!await cacheDir.exists()) {
+        await cacheDir.create(recursive: true);
+      }
+      Pdfrx.getCacheDirectory = () async => cacheDir.path;
+      debugPrint('[main] Pdfrx cache directory set to ${cacheDir.path}');
+    }
+  } catch (e, st) {
+    debugPrint('[main] Failed to initialize Pdfrx cache directory: $e');
+    debugPrint(st.toString());
+  }
+}
+
+Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
+  await _initPdfrxCache();
   // Disable right-click context menu on web using Flutter API
   if (kReleaseMode) {
     debugPrint = (String? message, {int? wrapWidth}) {

lib/routing/router.dart

@@ -33,7 +33,7 @@ final routerProvider = Provider<GoRouter>((ref) {
                 ({String? path, Uint8List? bytes, String? fileName}) =>
                     sessionVm.openPdf(
                       path: path,
-                      bytes: bytes,
+                      bytes: bytes ?? Uint8List(0),
                       fileName: fileName,
                     ),
           );

lib/ui/features/pdf/view_model/document_version.dart

@@ -0,0 +1,31 @@
+import 'dart:typed_data';
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'document_version.freezed.dart';
+
+/// Internal data model for tracking document versions in the UI layer.
+/// This is separate from the domain Document model to avoid coupling UI concerns with business logic.
+@freezed
+abstract class DocumentVersion with _$DocumentVersion {
+  const factory DocumentVersion({
+    @Default(0) int version,
+    Uint8List? lastBytes,
+  }) = _DocumentVersion;
+
+  factory DocumentVersion.initial() => const DocumentVersion();
+}
+
+extension DocumentVersionMethods on DocumentVersion {
+  /// Generate the source name for PdfDocumentRefData based on version
+  String get sourceName => 'document_v$version.pdf';
+
+  /// Check if bytes have changed and need version increment
+  bool shouldIncrementVersion(Uint8List? newBytes) {
+    return !identical(lastBytes, newBytes);
+  }
+
+  /// Increment version and update bytes
+  DocumentVersion incrementVersion(Uint8List? newBytes) {
+    return copyWith(version: version + 1, lastBytes: newBytes);
+  }
+}

lib/ui/features/pdf/view_model/pdf_view_model.dart

@@ -5,9 +5,11 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:pdf_signature/data/repositories/document_repository.dart';
 import 'package:pdf_signature/data/repositories/signature_card_repository.dart';
 import 'package:pdf_signature/domain/models/model.dart';
+import 'package:pdf_signature/ui/features/pdf/view_model/document_version.dart';
 import 'package:pdfrx/pdfrx.dart';
 import 'package:file_picker/file_picker.dart' as fp;
 import 'package:go_router/go_router.dart';
+import 'package:path_provider/path_provider.dart';
 
 class PdfViewModel extends ChangeNotifier {
   final Ref ref;
@@ -31,6 +33,26 @@ class PdfViewModel extends ChangeNotifier {
   final Set<String> _lockedPlacements = {};
   Set<String> get lockedPlacements => Set.unmodifiable(_lockedPlacements);
 
+  // Document version tracking for UI consistency
+  DocumentVersion _documentVersion = DocumentVersion.initial();
+
+  // Get current document source name for PdfDocumentRefData
+  String get documentSourceName {
+    // Ensure document version is up to date, but only update if really needed
+    _updateDocumentVersionIfNeeded();
+    return _documentVersion.sourceName;
+  }
+
+  void _updateDocumentVersionIfNeeded() {
+    final document = ref.read(documentRepositoryProvider);
+    if (!identical(_documentVersion.lastBytes, document.pickedPdfBytes)) {
+      _documentVersion = DocumentVersion(
+        version: _documentVersion.version + 1,
+        lastBytes: document.pickedPdfBytes,
+      );
+    }
+  }
+
   // const bool.fromEnvironment('FLUTTER_TEST', defaultValue: false);
   PdfViewModel(this.ref, {bool? useMockViewer})
     : _useMockViewer =
@@ -275,30 +297,59 @@ class PdfSessionViewModel extends ChangeNotifier {
     if (effectiveBytes == null && path != null && path.isNotEmpty) {
       try {
         effectiveBytes = await XFile(path).readAsBytes();
-      } catch (_) {
+      } catch (e, st) {
         effectiveBytes = null;
+        debugPrint(
+          '[PdfSessionViewModel] Failed to read PDF data from path=$path error=$e',
+        );
+        debugPrint(st.toString());
       }
     }
-    await openPdf(path: path, bytes: effectiveBytes, fileName: name);
+    if (effectiveBytes != null) {
+      await openPdf(path: path, bytes: effectiveBytes, fileName: name);
+    } else {
+      debugPrint(
+        '[PdfSessionViewModel] No PDF data available to open (path=$path, name=$name)',
+      );
+    }
   }
 
   Future<void> openPdf({
     String? path,
-    Uint8List? bytes,
+    required Uint8List bytes,
     String? fileName,
   }) async {
     int pageCount = 1; // default
-    if (bytes != null) {
+    try {
-      try {
+      // Defensive: ensure Pdfrx cache directory set (in case main init skipped in tests)
-        final doc = await PdfDocument.openData(bytes);
+      if (Pdfrx.getCacheDirectory == null) {
-        pageCount = doc.pages.length;
+        debugPrint(
-      } catch (_) {
+          '[PdfSessionViewModel] Pdfrx.getCacheDirectory was null; setting temp directory',
-        // ignore invalid bytes
+        );
+        try {
+          final temp = await getTemporaryDirectory();
+          Pdfrx.getCacheDirectory = () async => temp.path;
+        } catch (e, st) {
+          debugPrint(
+            '[PdfSessionViewModel] Failed to set fallback cache dir error=$e',
+          );
+          debugPrint(st.toString());
+        }
       }
+      final doc = await PdfDocument.openData(bytes);
+      pageCount = doc.pages.length;
+      debugPrint(
+        '[PdfSessionViewModel] Opened PDF bytes length=${bytes.length} pages=$pageCount',
+      );
+    } catch (e, st) {
+      debugPrint(
+        '[PdfSessionViewModel] Failed to read PDF data from bytes error=$e',
+      );
+      debugPrint(st.toString());
     }
     if (path != null && path.isNotEmpty) {
       _currentFile = XFile(path);
-    } else if (bytes != null && (fileName != null && fileName.isNotEmpty)) {
+    } else if ((fileName != null && fileName.isNotEmpty)) {
       // Keep in-memory XFile so .name is available for suggestion
       try {
         _currentFile = XFile.fromData(
@@ -306,8 +357,12 @@ class PdfSessionViewModel extends ChangeNotifier {
           name: fileName,
           mimeType: 'application/pdf',
         );
-      } catch (_) {
+      } catch (e, st) {
         _currentFile = XFile(fileName);
+        debugPrint(
+          '[PdfSessionViewModel] Failed to create XFile.fromData name=$fileName error=$e',
+        );
+        debugPrint(st.toString());
       }
     } else {
       _currentFile = XFile('');
@@ -322,13 +377,14 @@ class PdfSessionViewModel extends ChangeNotifier {
     } else {
       _displayFileName = '';
     }
-    ref
+    debugPrint('[PdfSessionViewModel] Calling openPicked with bytes');
-        .read(documentRepositoryProvider.notifier)
+    ref.read(documentRepositoryProvider.notifier).openPicked(bytes: bytes);
-        .openPicked(pageCount: pageCount, bytes: bytes);
     // Keep existing signature cards when opening a new document.
     // The feature "Open a different document will reset signature placements but keep signature cards"
     // relies on this behavior. Placements are reset by openPicked() above.
+    debugPrint('[PdfSessionViewModel] Navigating to /pdf');
     router.go('/pdf');
+    debugPrint('[PdfSessionViewModel] Notifying listeners after open');
     notifyListeners();
   }
 

lib/ui/features/pdf/widgets/pdf_page_area.dart

@@ -13,10 +13,12 @@ class PdfPageArea extends ConsumerStatefulWidget {
     super.key,
     required this.pageSize,
     required this.controller,
+    this.onDocumentChanged,
   });
 
   final Size pageSize;
   final PdfViewerController controller;
+  final void Function(PdfDocument?)? onDocumentChanged;
   @override
   ConsumerState<PdfPageArea> createState() => _PdfPageAreaState();
 }
@@ -163,7 +165,9 @@ class _PdfPageAreaState extends ConsumerState<PdfPageArea> {
         pageKeyBuilder: _pageKey,
         scrollToPage: _scrollToPage,
         controller: widget.controller,
-        innerViewerKey: const ValueKey('viewer_idle'),
+        // Remove fixed innerViewerKey to allow PdfViewerWidget to generate dynamic keys
+        // innerViewerKey: const ValueKey('viewer_idle'),
+        onDocumentChanged: widget.onDocumentChanged,
       );
     }
     return const SizedBox.shrink();

lib/ui/features/pdf/widgets/pdf_screen.dart

@@ -29,6 +29,8 @@ class PdfSignatureHomePage extends ConsumerStatefulWidget {
   // available, this name preserves the user-selected filename so we can
   // suggest a proper "signed_*.pdf" on save.
   final String? currentFileName;
+  // Optional listener for underlying Pdfrx document change events.
+  final void Function(PdfDocument?)? onDocumentChanged;
 
   const PdfSignatureHomePage({
     super.key,
@@ -36,6 +38,7 @@ class PdfSignatureHomePage extends ConsumerStatefulWidget {
     required this.onClosePdf,
     required this.currentFile,
     this.currentFileName,
+    this.onDocumentChanged,
   });
 
   @override
@@ -333,7 +336,7 @@ class _PdfSignatureHomePageState extends ConsumerState<PdfSignatureHomePage> {
                       pdf.loaded && pdf.pickedPdfBytes != null
                           ? PdfDocumentRefData(
                             pdf.pickedPdfBytes!,
-                            sourceName: 'document.pdf',
+                            sourceName: pdfViewModel.documentSourceName,
                           )
                           : null;
 
@@ -354,6 +357,7 @@ class _PdfSignatureHomePageState extends ConsumerState<PdfSignatureHomePage> {
                 controller: _viewModel.controller,
                 key: const ValueKey('pdf_page_area'),
                 pageSize: _pageSize,
+                onDocumentChanged: widget.onDocumentChanged,
               ),
             ),
       ),

lib/ui/features/pdf/widgets/pdf_toolbar.dart

@@ -5,6 +5,7 @@ import 'package:pdf_signature/l10n/app_localizations.dart';
 import 'package:responsive_framework/responsive_framework.dart';
 
 import 'package:pdf_signature/ui/features/pdf/view_model/pdf_view_model.dart';
+import 'package:pdf_signature/data/repositories/document_repository.dart';
 
 class PdfToolbar extends ConsumerStatefulWidget {
   const PdfToolbar({
@@ -59,7 +60,9 @@ class _PdfToolbarState extends ConsumerState<PdfToolbar> {
   @override
   Widget build(BuildContext context) {
     final pdfViewModel = ref.watch(pdfViewModelProvider);
-    final pdf = pdfViewModel.document;
+    final pdf = ref.watch(
+      documentRepositoryProvider,
+    ); // Watch document directly for updates
     final currentPage = pdfViewModel.currentPage;
     final l = AppLocalizations.of(context);
     final pageInfo = l.pageInfo(currentPage, pdf.pageCount);

lib/ui/features/pdf/widgets/pdf_viewer_widget.dart

@@ -5,6 +5,9 @@ import 'package:pdf_signature/l10n/app_localizations.dart';
 import 'pdf_page_overlays.dart';
 import './pdf_mock_continuous_list.dart';
 import '../view_model/pdf_view_model.dart';
+import 'package:pdf_signature/domain/models/document.dart';
+import 'package:pdf_signature/data/repositories/document_repository.dart';
+import 'dart:typed_data';
 
 // Provider to control whether viewer overlays (like scroll thumbs) are enabled.
 // Integration tests can override this to false to avoid long-running animations.
@@ -18,6 +21,7 @@ class PdfViewerWidget extends ConsumerStatefulWidget {
     this.scrollToPage,
     required this.controller,
     this.innerViewerKey,
+    this.onDocumentChanged,
   });
 
   final Size pageSize;
@@ -26,13 +30,43 @@ class PdfViewerWidget extends ConsumerStatefulWidget {
   final PdfViewerController controller;
   // Optional key applied to the inner Pdfrx PdfViewer to force disposal/rebuild
   final Key? innerViewerKey;
+  // External hook to observe document changes (forwarded from Pdfrx onDocumentChanged)
+  final void Function(PdfDocument?)? onDocumentChanged;
 
   @override
   ConsumerState<PdfViewerWidget> createState() => _PdfViewerWidgetState();
 }
 
 class _PdfViewerWidgetState extends ConsumerState<PdfViewerWidget> {
-  PdfDocumentRef? _documentRef;
+  final ValueNotifier<PdfDocumentRef?> _docRefNotifier = ValueNotifier(null);
+  Uint8List? _lastBytes;
+  void _updateDocRef(Document doc) {
+    if (!doc.loaded || doc.pickedPdfBytes == null) {
+      if (_docRefNotifier.value != null) {
+        debugPrint('[PdfViewerWidget] Clearing docRef (no document loaded)');
+        _docRefNotifier.value = null;
+      }
+      return;
+    }
+    final bytes = doc.pickedPdfBytes!;
+    if (!identical(bytes, _lastBytes)) {
+      _lastBytes = bytes;
+      final viewModel = ref.read(pdfViewModelProvider);
+      debugPrint(
+        '[PdfViewerWidget] New PDF bytes detected -> ${viewModel.documentSourceName}',
+      );
+      // Force a full detach by setting null first so PdfViewer unmounts even if the
+      // framework would otherwise optimize rebuilds with same key ordering.
+      if (_docRefNotifier.value != null) {
+        _docRefNotifier.value = null;
+      }
+      final newRef = PdfDocumentRefData(
+        bytes,
+        sourceName: viewModel.documentSourceName,
+      );
+      _docRefNotifier.value = newRef;
+    }
+  }
 
   // Public getter for testing the actual viewer page
   int? get viewerCurrentPage => widget.controller.pageNumber;
@@ -51,31 +85,9 @@ class _PdfViewerWidgetState extends ConsumerState<PdfViewerWidget> {
   @override
   Widget build(BuildContext context) {
     final pdfViewModel = ref.watch(pdfViewModelProvider);
-    final document = pdfViewModel.document;
+    final document = ref.watch(documentRepositoryProvider);
     final useMock = pdfViewModel.useMockViewer;
-    // trigger rebuild when active rect changes
+    _updateDocRef(document);
-
-    // Update document ref when document changes
-    if (document.loaded && document.pickedPdfBytes != null) {
-      if (_documentRef == null) {
-        _documentRef = PdfDocumentRefData(
-          document.pickedPdfBytes!,
-          sourceName: 'document.pdf',
-        );
-      }
-    } else {
-      _documentRef = null;
-    }
-
-    if (_documentRef == null && !useMock) {
-      String text;
-      try {
-        text = AppLocalizations.of(context).noPdfLoaded;
-      } catch (_) {
-        text = 'No PDF loaded';
-      }
-      return Center(child: Text(text));
-    }
 
     if (useMock) {
       return PdfMockContinuousList(
@@ -89,80 +101,119 @@ class _PdfViewerWidgetState extends ConsumerState<PdfViewerWidget> {
     }
 
     final overlaysEnabled = ref.watch(viewerOverlaysEnabledProvider);
-    return PdfViewer(
+    return ValueListenableBuilder<PdfDocumentRef?>(
-      _documentRef!,
+      valueListenable: _docRefNotifier,
-      key: widget.innerViewerKey ?? const Key('pdf_continuous_mock_list'),
+      builder: (context, docRef, _) {
-      controller: widget.controller,
+        if (docRef == null) {
-      params: PdfViewerParams(
+          String text;
-        onViewerReady: (document, controller) {
+          try {
-          // Update page count in repository
+            text = AppLocalizations.of(context).noPdfLoaded;
-          ref
+          } catch (_) {
-              .read(pdfViewModelProvider.notifier)
+            text = 'No PDF loaded';
-              .setPageCount(document.pages.length);
-        },
-        onPageChanged: (page) {
-          if (page != null) {
-            // Also update the view model to keep them in sync
-            ref.read(pdfViewModelProvider.notifier).jumpToPage(page);
           }
-        },
+          return Center(child: Text(text));
-        viewerOverlayBuilder:
+        }
-            overlaysEnabled
+        final pdfViewModel = ref.read(pdfViewModelProvider);
-                ? (context, size, handle) {
+        final viewerKey =
-                  return [
+            widget.innerViewerKey ??
-                    // Vertical scroll thumb on the right
+            Key('pdf_viewer_${pdfViewModel.documentSourceName}');
-                    PdfViewerScrollThumb(
+
-                      controller: widget.controller,
+        return PdfViewer(
-                      orientation: ScrollbarOrientation.right,
+          docRef,
-                      thumbSize: const Size(40, 25),
+          key: viewerKey,
-                      thumbBuilder:
+          controller: widget.controller,
-                          (context, thumbSize, pageNumber, controller) =>
+          params: PdfViewerParams(
-                              Container(
+            onViewerReady: (document, controller) {
-                                color: Colors.black.withValues(alpha: 0.7),
+              // Update page count in repository
-                                child: Center(
+              ref
-                                  child: Text(
+                  .read(pdfViewModelProvider.notifier)
-                                    'Pg $pageNumber',
+                  .setPageCount(document.pages.length);
-                                    style: const TextStyle(
+            },
-                                      color: Colors.white,
+            onPageChanged: (page) {
-                                      fontSize: 12,
+              if (page != null) {
+                // Also update the view model to keep them in sync
+                ref.read(pdfViewModelProvider.notifier).jumpToPage(page);
+              }
+            },
+            onDocumentChanged: (doc) async {
+              final pc = doc?.pages.length;
+              debugPrint(
+                '[PdfViewerWidget] onDocumentChanged called (pages=$pc)',
+              );
+              if (doc != null) {
+                // Update internal page count state
+                ref
+                    .read(pdfViewModelProvider.notifier)
+                    .setPageCount(doc.pages.length);
+              }
+              // Invoke external listener after internal handling
+              try {
+                widget.onDocumentChanged?.call(doc);
+              } catch (e, st) {
+                debugPrint(
+                  '[PdfViewerWidget] external onDocumentChanged threw: $e\n$st',
+                );
+              }
+            },
+            viewerOverlayBuilder:
+                overlaysEnabled
+                    ? (context, size, handle) {
+                      return [
+                        // Vertical scroll thumb on the right
+                        PdfViewerScrollThumb(
+                          controller: widget.controller,
+                          orientation: ScrollbarOrientation.right,
+                          thumbSize: const Size(40, 25),
+                          thumbBuilder:
+                              (context, thumbSize, pageNumber, controller) =>
+                                  Container(
+                                    color: Colors.black.withValues(alpha: 0.7),
+                                    child: Center(
+                                      child: Text(
+                                        'Pg $pageNumber',
+                                        style: const TextStyle(
+                                          color: Colors.white,
+                                          fontSize: 12,
+                                        ),
+                                      ),
                                     ),
                                   ),
-                                ),
+                        ),
-                              ),
+                        // Horizontal scroll thumb on the bottom
-                    ),
+                        PdfViewerScrollThumb(
-                    // Horizontal scroll thumb on the bottom
+                          controller: widget.controller,
-                    PdfViewerScrollThumb(
+                          orientation: ScrollbarOrientation.bottom,
-                      controller: widget.controller,
+                          thumbSize: const Size(40, 25),
-                      orientation: ScrollbarOrientation.bottom,
+                          thumbBuilder:
-                      thumbSize: const Size(40, 25),
+                              (context, thumbSize, pageNumber, controller) =>
-                      thumbBuilder:
+                                  Container(
-                          (context, thumbSize, pageNumber, controller) =>
+                                    color: Colors.black.withValues(alpha: 0.7),
-                              Container(
+                                    child: Center(
-                                color: Colors.black.withValues(alpha: 0.7),
+                                      child: Text(
-                                child: Center(
+                                        'Pg $pageNumber',
-                                  child: Text(
+                                        style: const TextStyle(
-                                    'Pg $pageNumber',
+                                          color: Colors.white,
-                                    style: const TextStyle(
+                                          fontSize: 12,
-                                      color: Colors.white,
+                                        ),
-                                      fontSize: 12,
+                                      ),
                                     ),
                                   ),
-                                ),
+                        ),
-                              ),
+                      ];
-                    ),
+                    }
-                  ];
+                    : (context, size, handle) => const <Widget>[],
-                }
+            // Per-page overlays to enable page-specific drag targets and placed signatures
-                : (context, size, handle) => const <Widget>[],
+            pageOverlaysBuilder: (context, pageRect, page) {
-        // Per-page overlays to enable page-specific drag targets and placed signatures
+              return [
-        pageOverlaysBuilder: (context, pageRect, page) {
+                PdfPageOverlays(
-          return [
+                  pageSize: Size(pageRect.width, pageRect.height),
-            PdfPageOverlays(
+                  pageNumber: page.pageNumber,
-              pageSize: Size(pageRect.width, pageRect.height),
+                ),
-              pageNumber: page.pageNumber,
+              ];
-            ),
+            },
-          ];
+          ),
-        },
+        );
-      ),
+      },
     );
   }
 }

lib/ui/features/welcome/view_model/welcome_view_model.dart

@@ -1,4 +1,4 @@
-import 'dart:typed_data';
+import 'package:flutter/foundation.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:pdf_signature/ui/features/pdf/view_model/pdf_view_model.dart';
 import 'package:go_router/go_router.dart';
@@ -11,6 +11,14 @@ class WelcomeViewModel {
   WelcomeViewModel(this.ref, this.router);
 
   Future<void> openPdf({required String path, Uint8List? bytes}) async {
+    // Return early if no bytes provided - can't open PDF without data
+    if (bytes == null) {
+      debugPrint(
+        '[WelcomeViewModel] Cannot open PDF: no bytes provided for $path',
+      );
+      return;
+    }
+
     // Use PdfSessionViewModel to open and navigate.
     final session = ref.read(pdfSessionViewModelProvider(router));
     await session.openPdf(path: path, bytes: bytes);

test/features/step/a_document_is_open_and_contains_at_least_one_signature_placement.dart

@@ -12,7 +12,7 @@ Future<void> aDocumentIsOpenAndContainsAtLeastOneSignaturePlacement(
 ) async {
   final container = TestWorld.container ?? ProviderContainer();
   TestWorld.container = container;
-  container.read(documentRepositoryProvider.notifier).openPicked(pageCount: 5);
+  container.read(documentRepositoryProvider.notifier).openPickedWithPageCount(pageCount: 5);
   container
       .read(documentRepositoryProvider.notifier)
       .addPlacement(

test/features/step/a_document_is_open_and_contains_multiple_placed_signature_placements_across_pages.dart

@@ -13,7 +13,7 @@ aDocumentIsOpenAndContainsMultiplePlacedSignaturePlacementsAcrossPages(
 ) async {
   final container = TestWorld.container ?? ProviderContainer();
   TestWorld.container = container;
-  container.read(documentRepositoryProvider.notifier).openPicked(pageCount: 5);
+  container.read(documentRepositoryProvider.notifier).openPickedWithPageCount(pageCount: 5);
   container
       .read(documentRepositoryProvider.notifier)
       .addPlacement(

test/features/step/a_document_is_open_with_no_signature_placements_placed.dart

@@ -11,6 +11,6 @@ Future<void> aDocumentIsOpenWithNoSignaturePlacementsPlaced(
   TestWorld.container = container;
   container
       .read(documentRepositoryProvider.notifier)
-      .openPicked(pageCount: 5);
+      .openPickedWithPageCount(pageCount: 5);
   // No placements added
 }

test/features/step/a_document_page_is_selected_for_signing.dart

@@ -11,7 +11,7 @@ Future<void> aDocumentPageIsSelectedForSigning(WidgetTester tester) async {
   // Ensure a document is open
   final repo = container.read(documentRepositoryProvider.notifier);
   if (!container.read(documentRepositoryProvider).loaded) {
-    repo.openPicked(pageCount: 5);
+    repo.openPickedWithPageCount(pageCount: 5);
   }
   // Ensure current page is 1 for consistent subsequent steps
   try {

test/features/step/a_multipage_document_is_open.dart

@@ -18,7 +18,7 @@ Future<void> aMultipageDocumentIsOpen(WidgetTester tester) async {
   container.read(signatureCardRepositoryProvider.notifier).state = [
     SignatureCard.initial(),
   ];
-  container.read(documentRepositoryProvider.notifier).openPicked(pageCount: 5);
+  container.read(documentRepositoryProvider.notifier).openPickedWithPageCount(pageCount: 5);
   // Reset page state providers
   try {
     container.read(pdfViewModelProvider.notifier).jumpToPage(1);

test/features/step/a_sample_multipage_document5_pages_is_available.dart

@@ -11,5 +11,5 @@ Future<void> aSampleMultipageDocument5PagesIsAvailable(
   TestWorld.container = container;
   container
       .read(documentRepositoryProvider.notifier)
-      .openPicked(pageCount: 5);
+      .openPickedWithPageCount(pageCount: 5);
 }

test/features/step/a_signature_asset_is_placed_on_the_page.dart

@@ -17,7 +17,7 @@ Future<void> aSignatureAssetIsPlacedOnThePage(WidgetTester tester) async {
   if (!container.read(documentRepositoryProvider).loaded) {
     container
         .read(documentRepositoryProvider.notifier)
-        .openPicked(pageCount: 5);
+        .openPickedWithPageCount(pageCount: 5);
   }
 
   // Get or create an asset

test/features/step/a_signature_placement_is_placed_on_page.dart

@@ -17,7 +17,7 @@ Future<void> aSignaturePlacementIsPlacedOnPage(
   if (!container.read(documentRepositoryProvider).loaded) {
     container
         .read(documentRepositoryProvider.notifier)
-        .openPicked(pageCount: 5);
+        .openPickedWithPageCount(pageCount: 5);
   }
   final page = param1.toInt();
   container

test/features/step/a_signature_placement_is_placed_with_a_position_and_size_relative_to_the_page.dart

@@ -16,7 +16,7 @@ Future<void> aSignaturePlacementIsPlacedWithAPositionAndSizeRelativeToThePage(
   if (!container.read(documentRepositoryProvider).loaded) {
     container
         .read(documentRepositoryProvider.notifier)
-        .openPicked(pageCount: 5);
+        .openPickedWithPageCount(pageCount: 5);
   }
   final currentPage = container.read(pdfViewModelProvider).currentPage;
   container

test/features/step/the_user_drags_it_on_the_page_of_the_document_to_place_signature_placements_in_multiple_locations_in_the_document.dart

@@ -25,7 +25,7 @@ theUserDragsItOnThePageOfTheDocumentToPlaceSignaturePlacementsInMultipleLocation
   if (!container.read(documentRepositoryProvider).loaded) {
     container
         .read(documentRepositoryProvider.notifier)
-        .openPicked(pageCount: 5);
+        .openPickedWithPageCount(pageCount: 5);
   }
 
   container

test/features/step/the_user_drags_this_signature_card_on_the_page_of_the_document_to_place_a_signature_placement.dart

@@ -21,7 +21,7 @@ theUserDragsThisSignatureCardOnThePageOfTheDocumentToPlaceASignaturePlacement(
   if (!container.read(documentRepositoryProvider).loaded) {
     container
         .read(documentRepositoryProvider.notifier)
-        .openPicked(pageCount: 5);
+        .openPickedWithPageCount(pageCount: 5);
   }
 
   // Get or create an asset

test/features/step/the_user_opens_a_different_document_with_pages.dart

@@ -19,7 +19,7 @@ Future<void> theUserOpensADifferentDocumentWithPages(
   // Simulate "open a different document": reset placements and set page count.
   container
       .read(documentRepositoryProvider.notifier)
-      .openPicked(pageCount: pageCount);
+      .openPickedWithPageCount(pageCount: pageCount);
   // Ensure there are 2 signature cards available as per scenario.
   final cards = container.read(signatureCardRepositoryProvider);
   if (cards.length < 2) {

test/features/step/the_user_places_it_in_multiple_locations_in_the_document.dart

@@ -12,7 +12,7 @@ Future<void> theUserPlacesItInMultipleLocationsInTheDocument(
   TestWorld.container = container;
   final notifier = container.read(documentRepositoryProvider.notifier);
   // Always open a fresh doc to avoid state bleed between scenarios
-  notifier.openPicked(pageCount: 6);
+  notifier.openPickedWithPageCount(pageCount: 6);
   // Place two on page 2 and one on page 4
   notifier.addPlacement(page: 2, rect: const Rect.fromLTWH(10, 10, 80, 40));
   notifier.addPlacement(page: 2, rect: const Rect.fromLTWH(120, 50, 80, 40));

test/features/step/the_user_savesexports_the_document.dart

@@ -17,7 +17,7 @@ Future<void> theUserSavesexportsTheDocument(WidgetTester tester) async {
     // Load a minimal sample so the expectation passes in logic-only tests
     container
         .read(documentRepositoryProvider.notifier)
-        .openPicked(pageCount: 2, bytes: Uint8List(10));
+        .openPickedWithPageCount(pageCount: 2, bytes: Uint8List(10));
   }
   expect(pdf.loaded, isTrue, reason: 'PDF must be loaded before export');
   // Check if there are placements

test/features/step/the_user_selects.dart

@@ -10,7 +10,7 @@ Future<void> theUserSelects(WidgetTester tester, dynamic file) async {
   final container = ProviderContainer();
   TestWorld.container = container;
   // Mark page for signing to enable signature ops
-  container.read(documentRepositoryProvider.notifier).openPicked(pageCount: 1);
+  container.read(documentRepositoryProvider.notifier).openPickedWithPageCount(pageCount: 1);
   // For invalid/unsupported/empty selections we do NOT set image bytes.
   // This simulates a failed load and keeps rect null.
   final token = file.toString();

test/features/step/three_signature_placements_are_placed_on_the_current_page.dart

@@ -22,7 +22,7 @@ Future<void> threeSignaturePlacementsArePlacedOnTheCurrentPage(
   container.read(signatureCardRepositoryProvider.notifier).state = [
     SignatureCard.initial(),
   ];
-  container.read(documentRepositoryProvider.notifier).openPicked(pageCount: 5);
+  container.read(documentRepositoryProvider.notifier).openPickedWithPageCount(pageCount: 5);
   final pdfN = container.read(documentRepositoryProvider.notifier);
   final page = container.read(pdfViewModelProvider).currentPage;
   pdfN.addPlacement(

test/widget/export_flow_test.dart

@@ -49,7 +49,7 @@ void main() {
           documentRepositoryProvider.overrideWith(
             (ref) =>
                 DocumentStateNotifier()
-                  ..openPicked(pageCount: 5, bytes: Uint8List(0)),
+                  ..openPickedWithPageCount(pageCount: 5, bytes: Uint8List(0)),
           ),
           pdfViewModelProvider.overrideWith(
             (ref) => PdfViewModel(ref, useMockViewer: true),

test/widget/pdf_thumbnail_sync_test.dart

@@ -0,0 +1,33 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pdf_signature/ui/features/pdf/view_model/document_version.dart';
+import 'dart:typed_data';
+
+void main() {
+  group('DocumentVersion', () {
+    test('should generate consistent source names', () {
+      final version1 = DocumentVersion(version: 1);
+      final version2 = DocumentVersion(version: 2);
+
+      expect(version1.sourceName, 'document_v1.pdf');
+      expect(version2.sourceName, 'document_v2.pdf');
+    });
+
+    test('should increment version when bytes change', () {
+      final bytes1 = Uint8List.fromList([1, 2, 3]);
+      final bytes2 = Uint8List.fromList([4, 5, 6]);
+
+      final version = DocumentVersion(version: 1, lastBytes: bytes1);
+
+      expect(version.shouldIncrementVersion(bytes2), true);
+      expect(version.shouldIncrementVersion(bytes1), false);
+    });
+
+    test('should detect identical bytes correctly', () {
+      final bytes = Uint8List.fromList([1, 2, 3]);
+      final version = DocumentVersion(version: 1, lastBytes: bytes);
+
+      // Same bytes object should not trigger increment
+      expect(version.shouldIncrementVersion(bytes), false);
+    });
+  });
+}

test/widget/welcome_drop_test.dart

@@ -51,7 +51,7 @@ void main() {
     }) async {
       final container = ProviderScope.containerOf(stateful.context);
       final repo = container.read(documentRepositoryProvider.notifier);
-      repo.openPicked(pageCount: 1, bytes: bytes);
+      repo.openPickedWithPageCount(pageCount: 1, bytes: bytes);
     }, [fake]);
     await tester.pump();