Andrew, hello!

I don't know of a way to save your own data to custom fields in a PDF file using InterSystems Reports.

As an option, I suggest you to consider creating a page with data you need for workflow on an additional page and export it to XML format together with the main PDF document.

So that the XML file would already be the controlling file for the handler.

I've added YouTube video and added it at the description of OEX Application
Also two related articles posted to DC, linked to application, please count.

And the last question is about bonuses for Tableau, PowerBI, Logi.

According to The Rules 3 points count for each of that systems.

I've used all them 3 in Contest App.