It seems to me that there's massive interest in this functionality and implementation shouldn't be too difficult - basically, it would be great if any ODF, PDF or ePUB document is uploaded it automatically becomes viewable within the chat area using one of the following Open Source scripts:

https://github.com/futurepress/epub.js/
http://viewerjs.org/

I don't have great JS chops so I can't unfortunately whip up a pull request but perhaps someone reading this could? Or alternatively maybe there's a quick way to automatically rewrite the URLs to document uploads and render them with these scripts just in Administration > Layout > Custom Scripts?

q./

ref: #2741 & #255