Upload Primary Content while Creating a WTDocument through REST API

I am no expert. We have a Customization area for these questions. Seems like Knowledge base has lots of articles on this:

https://www.ptc.com/en/support/article/CS18364?source=search

From what I know, its a multi-step process. Create the document, upload the file and linked it to the document. 

I never tried it, but with a batch process you should be able to create and upload the WTDocument in a single rest call. Unfortunately the olingo / odata batch process syntax is not that easy like creating a normal rest call and post a json.

https://support.ptc.com/help/windchill/r13.1.1.0/en/index.html#page/Windchill_Help_Center/WCRESTFramework/WCCG_RESTAPIsBatchSupport_examples.html