I assume that the desired functionality should act something like a PDF viewer.
I do not see how the RadEditor might come in handy for such a scenario. PDF files can only be viewed in the the browser, but cannot be editable.
I can suggest examining this blog post
, in which is demonstrated how you can use the PDF.js library and RadWindow to implement a PDF viewer.
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.