I'm amazed they don't get deleted when you restart your computer. I'm afraid it is a bit difficult to explain exactly where they are--I just did what you suggested with this web page, and got two temp files, the original pdf and the edited version. They are here:
/private/var/folders/Rv/RvRzJO5dHda62tPNz4CIxk
+TI/-Tmp-/printing.158/Preview of “Apple - Support - Discussions - where does Preview store the temp pdf ...”.pdf
/private/var/folders/Rv/RvRzJO5dHda62tPNz4CIxk
+TI/-Tmp-/printing.543/Preview of “Preview of “Apple - Support - Discussions - where does Preview store the temp pdf ...”.pdf”.pdf
In order to get there you need to first use the "Go" menu item "Go to folder..." and type in
/private/var/folders
and click the go button. You will see several folders with mysterious two letter names. You'll just have to open them and then open the sub-folder until you find the one that belongs to you. You can then trash the "printing.123" (or whatever number it has), and I do mean trash it--you need to actually EMPTY the Trash after you put the folder(s) in there. The name may still show up in the Recent list, but selecting it won't open a thing.
BTW, did you try just restarting?
Francine
Francine
Schwieder