Some lines on attached files are to thick. Other pdf programs shows that correctly. 

Regards
Janez

Provide a default appearance for fields that do not contain one. 

Workaround: set border and background manually:

var provider = new PdfFormatProvider();
var document = provider.Import(File.ReadAllBytes(@"..\..\..\Systemvariablen.pdf"));

foreach (var item in document.AcroForm.FormFields)
{ 
    var widget = item.Widgets.First() as VariableContentWidget;
     
    if (widget != null)
    { 
        widget.AppearanceCharacteristics.Background = new RgbColor(255, 0, 0);
        widget.AppearanceCharacteristics.BorderColor = new RgbColor(0, 0, 255);
        widget.Border = new AnnotationBorder(2, AnnotationBorderStyle.Solid, null);
      
        widget.RecalculateContent(); 
    }
}

pdfViewer.Document = document;

Changing the value of the DocumentSource property at runtime causes the RadPdfViewer to display a busy indicator and not update the displayed PDF file with the new one.

To work this around, derive from the RadPdfViewer and create a new dependency property for the property of the type of PdfDocumentSource (for example, from your view model). In its callback method, call the SetDocumentSource method of the derived RadPdfViewer by passing the new value:

public class MyPdfViewer : RadPdfViewer
{
    public PdfDocumentSource PdfDocumentSource
    {
        get { return (PdfDocumentSource)GetValue(PdfDocumentSourceProperty); }
        set { SetValue(PdfDocumentSourceProperty, value); }
    }

    public static readonly DependencyProperty PdfDocumentSourceProperty =
        DependencyProperty.Register("PdfDocumentSource", typeof(PdfDocumentSource), typeof(MyPdfViewer), new PropertyMetadata(new PropertyChangedCallback(OnDocumentSourceChanged)));

    private static void OnDocumentSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        MyPdfViewer viewer = (MyPdfViewer)d;

        viewer.SetDocumentSource((PdfDocumentSource)e.NewValue);
    }
}

<local:MyPdfViewer x:Name="pdfViewer" PdfDocumentSource="{Binding MyViewModelPropertyOfTypePdfDocumentSource}" />

The issue is closed as duplicated to the following item: http://feedback.telerik.com/Project/143/Feedback/Details/141105-tiling-patterns-are-rendered-wrong-when-some-transformation-is-applied

GoToPage() method is not working correctly in some cases when called in DocumentChanged event handler. The known cases are described below:

   1. When RadPdfViewer and the document are loaded initially and document is set through the RadPdfViewer.Document property.
Workaround: DocumentSource property could be set (in XAML or in code-behind) instead of the Document property. If the Document property is used, this should be done after RadPdfViewer is loaded.

    2. When the ScaleMode is changed in DocumentChanged event handler and then GoToPage() method is called in the same event handler.

The fix will be available in Q3 SP.