Thank you for your interest in Telerik RadRichTextBox!
Doc format is fairly outdated, therefore is with low priority in our to-do list. It depends on our road map and I couldn’t be more specific about the time frame when this might be implemented. At this point the feature is not scheduled.
I could only recommend you to convert your document to one of the supported by the control formats. You can find information about all the supported file formats and the providers in this article
Thank you for understanding.