After following these instructions I ended up with a working script that generates a pdf as I desire. Unfortunately, the text is only visible upon clicking the filled fields! (this only happens when using adobe reader, not when viewing the page through web browsers)
Seeing as users of the module aren't experiencing this issue I'm fairly certain it has something to do with the example script.
If I reassign the black text color in the generated pdf the text shows up as I want. So I'm assuming the issue has something to do with the textColor of the filled fields.
Any ideas how to solve this? (Can I assign field text color through pdfrw as a workaround?)