Another option that hasn't been mentioned yet is called Grand Avenue... google Grand Avenue Software for their website (I can't post links here yet
) The software includes different modules that can be implemented (or not implemented if you prefer)... including document management (also training, CAPA, complaints, non-conforming materials, etc.). It's 21CFR Part 11 compliant, and fully validated (company will give you their validation documentation if you request it). The document control module can also serve as your document change system... people sign on, review and approve document change requests, etc.
It's a pretty simplistic system, but also quite powerful... very affordable (payment is based on # of modules you activate and # of users). I have implemented this at two different companies, and their staff has always been extraordinarily helpful. I think it's a great system for small and some mid-sized companies... but probably not for bigger organizations.