In theory it would be possible to read the file using javascript and
render it. It can be done, with some browsers at least, for pdf files
and images. But I am not sure if there is such a library for office
files (maybe there is and I just don't know it)
If the OP has a javascript library at hand that does that for pptx,
docx, ... it would be doable. You could attach the action to the file
upload button in the document library.
