Make computed data available with Custom Form Action

Hello, i followed this tutorial to create a custom form action.
The action works, but in the run() method i compute some data i want to make available to other actions.

Consider for instance this use case:

The user submit a form. The custom action take a field with a post_id, generates a PDF of that post, and want to add the PDF URL to the response, so that i can use it in email action, activecampaing action, and so on.

What is the right ways to do this?