diff-pdf | A simple tool for visually comparing two PDF files | Document Editor library

The temp files disappearance are controlled by optional [--time TIME] variable, thus may have been deleted when you look if the setting is not high enough.

However the latest brew should have an extra optional ability to hold the files in a given location. Unsure if that was in latest release (possibly not).

The fact that your using VC suggests your using Windows and the likely location is a sub-folder in the %temp% directory, so watch that whilst running a compare and you should see a new folder at time of invocation.

It thus may be in something like C:\Users\your name\AppData\Local\Temp\diffpdfbzfxlraz or at run time some tmp files may be in a work area and built as /tmp/diffpdfhkhuea_s

You need to watch for both as there are different worksets built by the chained poppler and imgmagick, not to mention python or any windows env setting. See the docs for upping --time to say 600 seconds, whilst you searching.