TrackMyFiles from Iternum software automatically saves backup versions of files in specified directories on your hard drive. It goes beyond undelete software by allowing you to restore or view of your choice from among many previous file versions. So if you belatedly realize that you need a paragraph or slide you changed three saves ago, you can right-click the file and bring up the appropriate prior version. You can also restore deleted documents via the TrackMyFiles interface.
It's fastest to right-click and choose a version listed by date; but if you proceed through the program interface, you can instead select according to descriptive notes that you set for different versions, such as "Sent to Maureen." Iternum says that it saves only the changes made from one version to the next, which should use up far less backup space than storing multiple copies of the entire file as it evolves.
The program works with most file types, including Office documents, according to Iternum. It also handled changes that I made to a test bitmap image. You can try it free for 60 days, but after that it'll cost you $37 (not $35 as the site's FAQ says) to keep.
One piece of procedural advice: Put the TrackMyFiles download in its own folder before double-clicking to install it. If you run it from a folder that has a similarly named setup file, it will confusingly try to start that other program.