We use a digital archiving software in our office by Treeno systems..
http://www.treenosoftware.com/The system has been solid. It allows for version history as you had mentioned, along with putting workflows into place.
It can store multiple file types as well as allowing you to search documents by OCR if that would be helpful.
I can try to help with specific questions about it if you have some. The support has been terrific from this company as well.
It is basically like an unlimited virtual filing cabinet that you can store information into. The information can also be duplicated out into a tape, or DVD for offsite storage.
The software is extremely customizable if you have a programmer with some .php experience. The manufacturer also runs classes to help in training those individuals as well.