I convert 3D pdfs like this:
I get a 3D solid model in Solidworks, then I export to STL, then with Wings3D, I import .stl, then I export to .wrl. That .wrl file can be used by KICAD's 3D, however scaling and rotation is always wrong. So you have to change the rotation and X,Y,Z scales to match some known dimensions on the PCB layout. Often the scaling issues are a semi expected 25.4, or 10, some times they are simply crazy wrong.
HOWTO: make 3D models for KiCad
HOWTO: make 3D models for KiCad
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