From what I could gather, you're trying to embed RadDocument contents into a FlowDocument. RadDocument is designed to be used as a standalone, fully featured document format. Embedding it into other documents and embedding other documents in it is not in the focus of RadRichTextBox and the RadDocument model.
If you are trying to construct a document and then make it ready for printing, I'd recommend using the RadDocument API and/or RadRichTextBox as a means of creating a document and then using PDF exporting to print it. PDF is well spread and suitable for printing, so this should be a good solution to your problem.
PDF export should also work correctly under ASP.NET and you should be able to provider your users with a complete printing solution, preserving formatting completely.
FlowDocument and RadDocument are incompatible as they are based on completely different document models. If you require full pagination, text wrapping and so on, you should stick with one of them and implement all your functionality with it. The RadRichTextBox control with its RadDocument model is designed to be a superset of FlowDocument so you should be able to use them for anything you are used to do with FlowDocument. Let us know if we can assist you with implementing the functionality you currently have with our control.
If, however, XPS exporting is your end goal, we have planned two feature enhancements that will aid your scenario: XPS format provider and a format provider which converts to and from FlowDocument. When any of these features is available, what you are currently trying to do will become very easy.
the Telerik team
Registration for Q1 2011 What’s New Webinar Week is now open. Mark your calendar for the week starting March 21st and book your seat
for a walk through all the exciting stuff we ship with the new release!