public partial class FormWithWpfPdfTextSelectionTool : System.Windows.Window
{
    //...
    Vintasoft.Imaging.Wpf.UI.WpfImageViewer _imageViewer = null;
    Vintasoft.Imaging.Pdf.Wpf.UI.WpfPdfTextSelectionTool _textSelectionTool = null;
            
    //...
    public FormWithWpfPdfTextSelectionTool()
    {            
        //...
        // creates the PdfTextSelectionTool instance
        _textSelectionTool = new Vintasoft.Imaging.Pdf.Wpf.UI.WpfPdfTextSelectionTool(
            new System.Windows.Media.SolidColorBrush(System.Windows.Media.Color.FromArgb(56, 0, 0, 255)));
        // subscribe to text selection tool events
        _textSelectionTool.SelectionChanged += new System.EventHandler(_pdfViewerTool_SelectionChanged);
        _textSelectionTool.LinkClick += 
            new System.EventHandler<Vintasoft.Imaging.Pdf.Wpf.UI.PdfLinkEventArgs>(_pdfViewerTool_LinkClick);
        // sets the PDF text selection tool as current tool
        _imageViewer.VisualTool = _textSelectionTool;
    }
            
    //  Occurs when the _viewerTool.Selection is changed.
    private void _pdfViewerTool_SelectionChanged(object sender, System.EventArgs e)
    {
        if (_textSelectionTool.SelectedRegion != null)
            // show selected text
            System.Windows.MessageBox.Show(_textSelectionTool.SelectedRegion.TextContent);
    }
            
    // Occurs when the link is clicked. 
    void _pdfViewerTool_LinkClick(object sender, Vintasoft.Imaging.Pdf.Wpf.UI.PdfLinkEventArgs e)
    {
        switch (e.Action.ActionType)
        {
            case Vintasoft.Imaging.Pdf.Tree.PdfActionType.GoTo:
                // go to a destination in the current document
                _imageViewer.FocusedIndex = e.DestinationImageIndex;
                break;
            case Vintasoft.Imaging.Pdf.Tree.PdfActionType.Launch:
                // launch an application
                System.Diagnostics.Process.Start(((Vintasoft.Imaging.Pdf.Tree.PdfLaunchAction)e.Action).WinCommandLine);
                break;
            case Vintasoft.Imaging.Pdf.Tree.PdfActionType.URI:
                // resolve a uniform resource identifier (URI)
                System.Diagnostics.Process.Start(((Vintasoft.Imaging.Pdf.Tree.PdfUriAction)e.Action).URI);
                break;
        }
    }
}