Preview, by default, persists edits to the underlying file immediately. (i.e. if you crop something, the underlying file becomes cropped). I find this behavior very irritating.
I tried enabling Settings->General->"Ask to keep changes when closing documents". With this, Preview still persists the change to disk, but asks if I want to keep the change when I close the app.
A 2012 answer to a similar question suggested
defaults write -app 'preview' ApplePersistence -bool no
This does not seem to have any effect.
Is there any way to make Preview behave like a normal application? I want my changes unsaved and transient until I specifically hit save.