Check with Import diagnostic right after opening the catia file.
Set your graphic resolution. It does affect tesselation and 3D pdf file size
Run force rebuild.
I use export to IFC and import/convert to PDF with Bluebeam. That works better for large files.
I can copy paste individual components into self containing 3D view frames inside the PDF.
Try to eliminate and simplify before exporting as much as you can.
You can try to round-trip with IFC format. Breakout the asm into smaller subassemblies. Export out to IFC, then Import it back in again. Then create the 3D pdf from there. After import the files will be tesselated and sometimes this works to reduce the file size.
I believe Elmar is referring to the Image Quality settings (below). Moving the sliders to different positions and saving the 3D PDF a few times might help determine if its a tesselation issue.
You could try saving an STL to just to determine if the triangulated model might work if its generated a different way. Changing the angle to something like 3 degrees will reduce the # of triangles in the STL.