Upload Document (Method Set Entity File Services) doesn't appear in process webservices

Did you add the runtime reference to your project?

In the Web Service Interface Explorer, note the Web Service Operation's "Application / Organization" and "Web Service Interface". For UploadDocument it is "OpenText Entity Runtime" and "Method Set Entity File Services".

Now in your project, right-click on a folder and select "Add Runtime Reference | Other...". then select "Web Service Interface". In the dialog scroll down to the "OpenText Entity Runtime" package and select the "Method Set Entity File Services" method.

You will now have the method available to call in your BPM.