It looks to me like you have to add a form to each page of the existing document; i.e., I believe background images in PDF are really what they call forms. I'm not exactly sure how to do that from the examples though. It might be worth posing this question to the author of the module. That seems like a good example to have in the module tutorials/examples if it can be done.

I would probably start by trying to get to each page in the existing document individually, versus adding something to the entire document stream which seems to be what your example is doing.

In reply to Re: Add watermark to a pdf by steves
in thread Add watermark to a pdf by holli

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