Sometimes in life I have wondered...
"How the Hell did I get here?"
I my never get my answer, but with the files I share with AutoCAD WS, I can always use the Timeline feature to browse through each version as my design progresses.
You can even revert to an old version with this feature. There is a lot more on the AutoCAD WS page, with tutorials on how to use it.
And, because I used the movie reference, here's a nice picture to look at. Vrroom, vrooom!