Please turn off auto save!

Which application specifically? As far as I can tell, this depends on how the application is programmed.

Some may offer you the choice, some will work as you expect, and some save both versions the same (ie. keep the changes in the original file as well as the one you Save As...)

If you edit a file in the Pages app, then Save As, the dialogue box that pops up asks if you want to keep changes to the original document. If you deselect it, the changes won't appear on the other file.

Barney-15E wrote:

... Possibly a bug ...

It's not a bug. It's intentional design by Apple. Seven or eight years ago Apple introduced what they called, at the time, "modern document management." (You may recall the furor when "Save As" disappeared from many Apple apps.) That's when Apple introduced this practice.

It was (is) intended to preserve the current state of a document at all times. The problem, and I consider it a huge problem, is exactly what Cartoonguy complained about. It's an overt change from all prior and intuitive practice that can leave the user with undesired edits/changes to a document, especially if they don't know about this "feature." And getting around it requires multiple extra undocumented and little known steps.

Apple eventually backed off and returned "Save As" to most of its app menus. But the underlying, invisible and ongoing save behavior has remained.

I never felt the old way was intuitive at all. Save as what? Maybe a banana?

Or, more intuitive, save as another file format. Overwriting a document intending to later Save As… Oops, I hit Save. Rife with the potential to lose data. Versions, Duplicate all make much better sense.

Duplicate the document before you change it.

Or, Duplicate after making changes, then revert to the version you want.

At least Versions still works so you can recover what you overwrote.

Yeah, I don't know why it does that. Possibly a bug, but then Versions seems to work which I wouldn't expect. I thought that disabled Versions, too. Maybe it never did disable Versions.

The bug was in reference to keeping the changes. If there was a checkbox to revert changes, I missed it, too.