I helped grow an engineering company from 3 people to 25 with a mandate to provide for satellite offices and remote non-technical workers. SVN/Tortoise was the hammer I chose, because it was the only hammer I knew at the time that was even vaguely like a Document Management System.
It solved many of the basic problems, but it has not been without pain. Try explaining to a receptionist how to mitigate a tree-conflict error that she didn't cause. Worse, explaining to the satellite offices that video files require an entirely different sharing mechanism simply because they're big. To the president that his edits don't get priority over the guy who committed first.
If I had it to do over again with a shoestring budget, I'd probably do the same thing. But I'm here in this thread because I'm hoping there are better answers for people on the Linux server - windows client model, who have grown to the size where they have an IT budget, and place a high value on uninterrupted productivity.
So seriously, are there anecdotes from mid-size companies trying to solve the document management problem?