public Form2()
{
    InitializeComponent();    
    this.radPdfViewer1.PdfViewerElement.AnnotationClicked += RadPdfViewer1_AnnotationClicked;
}
private void RadPdfViewer1_AnnotationClicked(object sender, Telerik.Windows.Documents.Fixed.Model.Annotations.EventArgs.AnnotationEventArgs e)
{
    Telerik.Windows.Documents.Fixed.Model.Annotations.Link link = e.Annotation as Telerik.Windows.Documents.Fixed.Model.Annotations.Link;
    if (link == null)
    {
        return;
    }
    Telerik.Windows.Documents.Fixed.Model.Actions.Action linkAction = link.Actions?.FirstOrDefault();
    if (linkAction is GoToAction goToAction)
    {
        ExecuteGoToAction(this.radPdfViewer1,goToAction);
    }
           
}
private static void ExecuteGoToAction(RadPdfViewer presenter, GoToAction action)
{
    var viewer = presenter;
    if (action.Destination != null)
    {                
        presenter.PdfViewerElement.GoToDestination(action.Destination);
    }
    else if (action.NamedDestination != null)
    {
        if (action.NamedDestination.Destination != null)
        {
            presenter.PdfViewerElement.GoToDestination(action.NamedDestination.Destination);
        }
        else
        {
            ExecuteGoToAction(presenter, action.NamedDestination.GoToAction);
        }
    }
}