This missing functionality may be workaround by implementing and registering custom IPdfFilter implementation that decodes JPEG2000 images. The custom decoder may be registered with FiltersManager class and its implementation may be similar to RadPdfViewers JpxDecoder SDK example implementation:

- https://github.com/telerik/xaml-sdk/blob/master/PdfViewer/CustomDecoder/JpxDecoder.cs
- Use a custom JPXDecode filter with RadPdfViewer