Something that may not be obvious...you do not need a STEP worker to create STEP files from CAD files (Creo parts, assemblies, etc.). The normal proe2pv worker (for Creo/Pro-e files) can be configured to generate many different additional file formats, including STEP (via publish rules on the server). You only need the STEP worker if you are storing DOCUMENTS (not CAD documents) in Windchill with their primary content being STEP files. From what I understand, this is the only time a dedicated STEP worker will ever be used.
See last line of this: https://www.ptc.com/appserver/cs/view/solution.jsp?n=CS79209