Automator script: add header from user text

Question

I make a lot of flash cards in my work, and I'm looking to create a workflow to automatically stamp each with the relevant textbook and unit number. So far I've got as far as to open the pdf file from user input and I think the best way to go would be to get the text, then banner image to text, then watermark pdf. I haven't been able to get the watermark pdf action to take input from the previous action.