How about saving the changed document under a different name;
when I'm unsure of changes, I'll save a document with a -
following the name then
when I return to the documents I have the first, unchanged
one, and the working one with that - following it.
In this way, you can make any number of changes by merely adding
additional -s (or choose any character);
these will all be saved together so you can promptly see how
many, etc.
Just another KISs solution