You could use Google Doc Viewer through an iframe and specify the DOC, XLS or PDF file you want to display. This is the code you should add:
<iframe src="http://docs.google.com/gview?url=YOUR_ABSOLUTE_URL_TO_THE_FILE_HERE&embedded=true" style="width:600px; height:500px;" frameborder="0"></iframe>
Then you just need to set up your own document file to the "url" query string param and that's it!