Subversion, CVS and all other source control systems are not good for Word documents and other office files (such as Excel spread sheets), since the files themselves are stored in a binary format. That means that you can never go back and annotate (or blame, or whatever you want to call it), or do diffs between documents.
There are revision control systems for Word documents out there, unfortunately I do not know any good ones. We use such control systems for Excel at my work, and unfortunately they all cost money.
The good thing is that they make life a lot easier, especially if you ever have to do an audit or due diligence.