ProEpro is right. We use truEvault and are very happy with it. As long as you keep in mind that you are paying thousands less than Intralink and Windchill, then truEvault becomes a very viable alternative, and allows for an upgrade path to something else in the future once a different alternative presents itself.
(truEvault doesn't store the files itself, it only monitors and manages files in a selected location and tells you whether they are the proper revision or not...while Intralink takes the files and stores them as a proprietary, unreadable format - which ties you down to using Intralink now and forever)
Recneps