YES, it's applicable! I totally agree to say that the combo SVN+TortoiseSVN suits well to track MS Office documents. You can lock a document for edition, write protect all unlocked files to avoid conflicts (i.e. parallel modifications), diff two versions of the same file, see the history of all the modifications and of course rollback to an older revision.
I tried to describe all of those tips in a dedicated blog post. (disclaimer: I'm the blog owner)
All of this could even be accessible from the web with a SVN web client! (might need some software development)
But if you're not accustomed to Version Control Systems in an other context this may not be the obvious choice. The needed work for a good integration with docs give dedicated tools an advantage: "electronic document management" systems are made just for that. A VCS like SVN may stay a good alternative for cost reasons :-)
Did you test the online service Simul? It looks promising, I personally like the GitHub-like orientation. Note that I'm not affiliated to Simul!