RadEditor is a standard HTML/XHTML editor and it does not offer the requested RTF / Word import and export support out-of-the box, because the browser does not support this types of formatting itself.
In order to implement your scenario you should use some third party tool to convert the RTF / Word content to HTML markup and load it in RadEditor via its Content property. For your convenience I have found the following tools in Google:
You can find more tools in Google: http://www.google.bg/search?q=word2html&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
the Telerik team