But for you (in your PDF viewer) they work OK inc. viewport links? How do they work for other engineers/architects (not in that municipality)? Did you use Bluebeam or other good software to print out of Revit?
Sounds like a "them" problem and their likely outdated software. Did you ever talk to them what they use? On very rare occasions I got PDF from a vendor that look fine in bluebeam, But when I send these very same files to our accountants, who use Adobe, they showed me screenshots how they look blank or all scrambled. My workaround was to "print" them from Bluebeam. I talked to that vendor who sent those, and they reported they use a proprietary accounting software that creates those (I don't think the person was computer-literate, though). So yes, there can be file format issues, but not on up-to-date software. Maybe create the PDF out of Revit, and then print it from Bluebeam. Or use one of the Revit plugins (diroots etc.). Some people use very odd and old computer setups (fonts etc.) and such issues can happen.
You probably can crate a PDF of the very same set from Revit, and one with AutoCAD and have someone knowledgeable look at both files and tell what the difference is on a file formal level.
Before spending time on AutoCAD, I would explore ALL options to create acceptable PDF in a more direct way.
Revit Version: R2026.2
Hardware: i9 14900K, 64GB, Nvidia RTX 2000 Ada 16GB
Add-ins: ElumTools; Ripple-HVAC; ElectroBIM; Qbitec