The unsupported features include:
Almost all fonts that are embedded in the PDF file should be displayed correctly. There are minimal limitations with some font formats.
There are some limitations with CCITTFaxDecode filter.
JPXDecode filter: This filter does not work out of the box. However, there is API allowing to plug-in custom user-defined filters. This API is described in the Customize PDF Rendering topic and an SDK example showing the approach is available in our SDK repository on GitHub.
Annotations: Full support for Widget and Link annotations. All other types of annotations are supported in read-only mode.
Structured content: There are several ways to define structured content in a PDF file. RadPdfViewer does not support article threads. When a PDF file contains some of these items, it may be shown incorrectly or not shown at all.