how do I convert 3d pdf and .stl to .step
3 Answers

This is a very simple model to recreate.
Use this guide/tutorial: Convert STL (or OBJ) Mesh to SOLIDWORKS Model (NURBS)
Remake the model in your favorite software. It should not take much more than an hour.

It is possible with Tetra4.
https://tetra4d.com/tetra-4d-converter/
Very expensive for one time use.