I tried opening a PDF file in Preview, rotating a page to the right, and then saving the file. It said "The document ... could not be saved." I looked for console message and could not find any related. While I'm a software developer, I don't develop for Macos; I'm more of an end-user.
I checked permissions. The file and the containing folder are owned and writable by my user.
$ ls -la
total 1059
drwxrwxr-x 3 carl staff 3 Mar 29 21:19 .
drwxr-xr-x 8 carl staff 8 Mar 29 20:16 ..
-rw-r--r-- 1 carl staff 398564 Mar 29 21:19 1099-B.pdf
I can export the modified PDF to my Desktop, open and edit it from there, and then drag it to the ZFS filesystem folder using Finder. From there, I can open it in Preview and see the changes.