I'm looking for something similar. At the moment we use a combination of tutos (a groupware with integrated bugtracking system) and a normal BBS (phpBB). But actually I'm more than unhappy with this. I guess with some work tutos can be adapted for such a task but we don't have the manpower to do it atm.
Maybe you can check it out anyway. It's got doc management and everything you need. Only I find it rather unintuitive and it has some rough edges still which probably is the reason that many users on our site don't really use it. :-\