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" />

In Adobe and Foxit readers, the user can draw different shapes, which are later saved as images in the document.

The images are loaded asynchronously and when scrolling too fast, the loader might fail to load an image if it is bigger.

When users do "copy" operation, add the content to the clipboard in RTF format. This would allow to paste the text along with its formatting in text editors like MS Word.

The appearance of such invisible annotation is not imported property and the viewer is trying to recalculate it in an infinite recursion which causes the StackOverflowException.

Fix available in LIB Version 2017.3.1009.

Introduce support for Sticky Note Annotation.

Introduce support for PolyLine Annotation

Introduce support for Polygon Annotation

Introduce support for Circle Annotation

Introduce support for Square Annotation

Introduce support for Line Annotation.

They are used by the page and the XObjects drawn on it and deal with the overlaying of the colors. These groups are described on page 556 of PdfReference 1.7. 

The UserDict collection is not parsed and the procedures for the operators are unavailable. The exception is thrown while trying to read the font file of the Univers and Univers Bold fonts.

Internally, an ArgumenNullException is thrown, which results in missing content when the document is shown in RadPdfViewer.

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.

RadPdfViewer does not read image resources defined in Form XObject elements.

Default DctDecode implementation uses System.Windows.Media.Imaging.BitmapImage in order to get the image pixels. However, when the image uses some complex colorspace (for instance Separation based on CMYK) the BitmapImage is initialized with a different format and we use System.Windows.Media.Imaging.FormatConvertedBitmap in order to get the pixels in CMYK colorspace. There seems to be some issue with these calculations as the resulting image has incorrect pixels.

WORKAROUND: You may inherit DctDecode class in order to implement custom decoder and call 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 annotations have annotation flag Print they should be visualized when printing the document. Usually, Widget annotations have such flag and currently RadPdfViewer does not print them at all.

Available in LIB Version 2017.3.918.

NullReferenceException is thrown when importing a document with AcroForm referencing a missing object for fields collection. This is a regression as the same document will be imported without a problem in previous versions of RadPdfViewer as the AcroForm object would be entirely skipped.

The redaction annotation is described in the following PDF reference document:
http://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/pdf_reference_addendum_redaction.pdf

You may also see sample document with this annotation type attached.

Since LIB Version 2017.3.925 annotations of type Redact can be visualized.

The current implementation relies on the graphic state color to be always SolidColorBrush. However, it may be other color type and InvalidCastException is thrown. This results in missing content.

Available in LIB version 2017.1.410.