private void _toolManager_AnnotationAdded(Annot annotation)
        {
            // Update viewer after annotation added
            PDFViewer.Update(annotation, PDFViewer.GetCurrentPage());

            ResultSnapshot snap = _undoManager.TakeSnapshot();
        }
        private void AddTextSample()
        {
            var  workingDoc = PDFViewer.CurrentDocument;
            Page page       = workingDoc.GetPage(PDFViewer.CurrentPageNumber);

            if (page == null)
            {
                return;
            }

            _toolManager.CreateTool(ToolManager.ToolType.e_sticky_note_create);

            PDFViewer.Update();
        }
        private void Redo()
        {
            if (_undoManager == null)
            {
                return;
            }

            if (!_undoManager.CanRedo())
            {
                return;
            }

            _undoManager.Redo();

            PDFViewer.Update(); // PDFViewer updates display
        }