The issue occurs when RadPdfViewer is measured in infinite space, for example:
- Added to StackPanel.
- Added to RadWindow with Auto dimensions.

Workaround: Width and Height of RadPdfViewer can be set.

Some of the lines that should be dashed are rendered as continuous lines.

When Find Next is used multiple times fast, and pages are still loaded asynchronously, sometimes NullReferenceException is thrown with the following call stack:

System.NullReferenceException: Object reference not set to an instance of an object.
   at Telerik.Windows.Documents.Fixed.Text.TextRecognizer.GetLastCharacter()
   at Telerik.Windows.Documents.Fixed.Text.TextRecognizer.IsLineBreak(Glyph glyph)
   at Telerik.Windows.Documents.Fixed.Text.TextRecognizer.ProcessGlyph(Glyph glyph)
   at Telerik.Windows.Documents.Fixed.Text.TextRecognizer.CreateTextPage(RadFixedPageInternal page)
   at Telerik.Windows.Documents.Fixed.Text.TextDocument.GetTextPage(Int32 index)
   at Telerik.Windows.Documents.Fixed.Search.KMPTextSearch.FindNext(TextDocument document, TextPosition startPosition, String searchText, Boolean matchCase, Boolean wholeWordsOnly)
   at Telerik.Windows.Documents.Fixed.Search.TextSearch.Find(String text, TextSearchOptions options)

...

The issue is reproducible only on Windows XP. On newer versions of windows, the images are rendered as expected.

WORKAROUND: You may inherit DctDecode class in order to implement custom decoder. For instance, you may try calling DecodeWithJpegDecoder method from the base class as mentioned in the note of this documentation article:

http://docs.telerik.com/devtools/wpf/controls/radpdfviewer/customization-and-extensibility/customize-pdf-rendering

A sample implementation of these custom decoder may be seen below:

public class CustomDctDecode : DctDecode
{
    public override byte[] Decode(PdfObject decodedObject, byte[] inputData, DecodeParameters parms)
    {
        return DecodeWithJpegDecoder(inputData);
    }
}

When ScaleMode is set to FitToPage scrolling the Mousewheel or pressing the Arrow Down button does not produce immediate scroll. The page is scrolled to the next page after several scroll events/button presses are introduced.

Workaround: Provide custom ScrollCommand implementation.

This is reproducible when the matched result resides on different page.

Workaround: You may subscribe to the RadFixedDocument.CaretPosition.PositionChanged event and implement the scroll logic. Subscribe to PdfViewer's DocumentChanged event first if the document is not loaded.
        private void CaretPosition_PositionChanged(object sender, EventArgs e)
        {
            Telerik.Windows.Documents.Fixed.Model.RadFixedPage currentPage = this.pdfViewer.Document.CaretPosition.Page;
            int pageIndex = this.pdfViewer.Document.Pages.IndexOf(currentPage);
            this.pdfViewer.GoToPage(pageIndex + 1);
        }

Setting Handle property to false should result in rethrowing the exception and interrupting current RadFixedDocument rendering. This is related to Exception Handling Mechanism mentioned in this documentation article: 

https://docs.telerik.com/devtools/wpf/controls/radpdfviewer/document-model/exceptionhandling

FixedDocumentSinglePagePresenter uses simple rendering mechanism using UIElements, which currently has some limitations:
- Layers are not supported, thus annotations and forms are not rendered (even read-only)
- UIElements could be affected (clipped) when UseLayoutRounding property set at parent level, when DPI is different that 96 DPI. 

Workaround: If content is clipped, ensure that UseLayoutRounding is set to false as presenter level:
<telerikUI:FixedDocumentSinglePagePresenter UseLayoutRounding="False" />

This may result in seeing the pattern as a solid color or even not seeing it at all if this color is white and coincides with the background of the page.