The latest official version of the RadEditor (2014 Q2) supports importing of RTF document that can be edited and after that again exported to RTF. You can see how to implement such functionality in this demo.
Also, for the next official release (2014 Q3) the RadEditor will be improved with new exporting functionality that eliminates some existing limitations of the RTF import/export, and will support DOCX. At this moment, you can test the upgraded feature via the beta demos:
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