For making your CAD file to low-poly you need first to convert it into .obj or .stl. It is described in this tutorial.
If you have and .obj or .stl file you can use the Fast-Quadric-Mesh-Simplification tool. You need to clone the git repository (https://github.com/sp4cerat/Fast-Quadric-Mesh-Simplification) or use the online version, found here.
With the online version you can easily upload your file and then to select the simplification rate. After downloading the low-poly file it is Apertus ready.