The PDF document with images shows black canvas:

NOTE:

Works OK in version 2023.2.713
Broken in version 2023.3.1005

Introduce events similar to the PageRenderStarted and PageRenderCompleted ones that the Telerik UI for WinForms RadPdfViewer provides:

WinForms PdfViewer How-To Handle Rendering Events - Telerik UI for WinForms

The edited value of an interactive form field (for example TextBox) is not committed when the form goes outside of the viewport while still in edit mode.

OutOfMemoryException has thrown when creating a thumbnail with the ThumbnailFactory.

This behavior is observed with binaries version 2020.2.513 or later.

The size of some images in specific documents is scaled and positioned wrongly.

Expose API that allows you to add/remove Annotations/IPointerHandler implementations from the PointerHandlersController.

Currently, RadPdfViewer doesn't allow you to render notes/comments added to the highlight annotations. Add the option to render this and possibly allow editing. 

The path objects are not drawn with correct background.

When displaying PDF-Files using PDFViewer, ContentElementsCanvas .RenderAsync uses reflection (DispatcherObjectUtils.ApplyDispatcher) to render Visuals on multiple threads.
However this leads to a memory leak since the dispatchers cant be GC'ed, see screenshot below.




The Screenshot is from the actual application we expirienced this issue with, the attached reproduction example is a boiled down version of what your code does.
If you wanna reproduce this on your own, create an application that uses PdfViewer that switches between many pdf files. The ammount of Dispatchers will grow steadily, probably to a total of the number of threads used by Task.Factory.

Add support for handwritten (graphometric information) signatures in the PdfViewer. 

PDF Signature(image) is displayed on the incorrect location when using annotations.

Wrong color of lines due to Matrix Transformations applied to the Drawing.

Some lines could be missing in the PdfViewer when rendering line geometries.

The attached image shows the issue.

The import performance is reduced and the memory consumption is increased when XObject instances have many Shading elements.

Glyphs with specific font added to the document are not rendered. 

Layers represent groups of optional content which can be hidden or shown.

PdfViewer: The selected page is not synchronized with the selected index in the Thumbnail view when a document is opened manually. This issue occurs in the thumbnail example in the demo applicationl. 

The default WPF PrintDialog cannot print asynchronously when it is shown in UI. However, you may see the demo in this forum post showing how to create custom PrintDialog and perform async printing with it:
http://www.telerik.com/forums/pdfviewer-print-makes-ui-unresponsive#js0YdzFWc0Oa8C3g6a18lg

Currently, the Save button of the RadPdfViewerToolBar element raises the SaveAsPdfDocumentCommand, which opens a new SaveFileDialog in its Execute method. We could raise an event there, in order for this action to be intercepted if the PDF file is saved.

Images hosted inside multiple Form XObjects are not rendered.