RadRichTextBox is intended exactly for showing/modifying flow documents from different file formats and I believe it could fit your scenario.
The ScrollViewer measures its children with Infinity, thus, the RadRichTextBox instance doesn't receive a particular size in which it should fit. This leads to stretching the control, the document receives enough space to load its whole content and the scroll bars aren't activated. If you change the container you are using to a different one that sets a size to its children (for example, Grid), you should be able to use the scrolling of the control.
In addition, we usually advise against measuring RadRichTextBox in Infinity as this will disable the UI Virtualization
of the control and could lead to performance diminishments or unexpected behavior.
In regards to the export functionalities, you could refer to our Import/Export section
that describes the supported in RadRichTextBox formats and how to use them.
Hope this helps.
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