Some notes on using "FreeCAD".  It can open and manipulate STEP files (and probably many other things).
These notes apply to version 0.18.1.

== Making a 2D drawing from part of a model

* Use the new TechDraw workbench module: 
 * Wiki: https://www.freecadweb.org/wiki/TechDraw_Module
 * Tutorial: https://www.freecadweb.org/wiki/Basic_TechDraw_Tutorial

Tip:  to open a new workbench, click on the "mode" thingy:

[[Image(http://ohm.bu.edu/~hazen/FreeCAD/Screenshot_2019-05-02_09-31-35.png)]]