OK not strictly Office software, but it does clain to assist with working with Office documents etc [sorry if this is in the wrong forum]
I haven't tried this yet [havent had the chance] but I wanted to post this before I forgot about it.
The site says:
"ShowDocument is a nitfy little web service that provides live and free document sharing. Itís super simple to use and requires no downloads or installations in order to work! You can upload a document and invite others to view and discuss it."
I have had staff request this type of sharing in the past and I had no way for making it happen for them. No download/install and it is free!
Link here: Link