There is no specific version of PDF we are supporting. If the PDF file is created by certain rules you will be able to open it in the RadPdfViewer no matter its version. However, we are working on expanding our range of supported documents for the upcoming versions of the control.
You can open a support ticket and attach sample documents which are not imported in the control, so that we can investigate the cause and be more specific about the timeline of when they could be opened.
the Telerik team
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