Mac: crashes occur when program language differs from OS language
For years I experienced crashes when saving documents that had backgrounds graphics added in Acrobat. The bug was triggered by the fact, that my os language was english and my Acrobat language preferences were set to German. (see https://acrobat.uservoice.com/forums/590923-acrobat-for-windows-and-mac/suggestions/39351328-program-crashes-while-saving-after-background-has)
If you are experiences similar problems, make sure to set your program language to the same language as your OS.
It's a very nasty and confusing problem. I hope it will be fixed in the future.
Sorry for the issue that you are facing while saving the PDF.
Could you please share the Crash report that appears after Acrobat crashes for you on you Mac system ?
That’ll help us to triage this issue further.