Create WTDoc with content with REST API

I am using Windchill PDMLink Release 12.1 and Datecode with CPS 12.1.2.1 I want to create a Document using REST API, while adding a PDF as primary content and another file as secondary content. I know how to create iteration 0.1 of the Document, then add the files to iteration 0.2. How can I create everything in iteration 0.1? Here are the errors that I faced self.url + "/servlet/odata/DocMgmt/UploadStage1Action with data { "NoOfFiles": 1} gives error: ApiError NOT FOUND 404 self.url + "/servlet/odata/DocMgmt/PTC.DocMgmt.UploadStage1Action with data { "NoOfFiles": 1} gives error: UploadStage1Action must not follow a collection