I installed Stirling PDF a while ago - its a complete toolkit for working with PDFs. The downside is it is meant to be run on a server within docker, but its straightforward enough to do this in Zorin.
The free (self-hosted) version gives you all the same tools as the Pro, just minus support.
There was a thread in this forum on installing it:
But you are better (once you have installed docker...) to go here:
https://docs.stirlingpdf.com/Installation/Docker%20Install/