A Reverse Save Function

I regularly work on projects that require I save different versions throughout the overall process--often, we'll decide to go one direction, delete a bunch of slides, and then reverse the decision and need to put them back in. And on more than one occasion, I've automatically saved without remembering to change the document title, sending those precious slides to the document junkyard, broken pixel by pixel into meaningless & nothingness.

Usually, I realized I've done this almost immediately after I've saved. Now I know there are things like TimeMachine on Mac that save me from this fate, but it changes EVERYTHING on my computer back to how it had been. Why can't Ctrl+Z also reverse a save???