Macarena - back when I used to work for another company, we used to use a tool (AppendPDF Pro – Appligent ) to do something similar. Our use-case was to provide digital, personalized/custom PDFs at our event booths (rather than printed collateral). A user would interact with a tablet or laptop - filling out a simple form (name, company, email, country) which also included a listing of related collateral/PDFs. For example, if we were exhibiting at SAPPHIRE or Oracle Open World, we would provide a listing of all of our SAP- or Oracle-related PDFs. Once a user ticked off the appropriate checkboxes next to each PDF - and submitted the form - a personalized PDF file (branded title page with their name/company, personalized table of contents, followed by all of the PDFs they selected, appended to a single PDF file) was emailed to them immediately.
Sure, as I usually say, why not?
It's a matter of setting the URL to the PDF generator (not a PDF per se, though the response will be a PDF) to include identifying information, such as a link to a CO record or simply flat lead record, that the generator can use to pull data from Marketo. Or, if this applies, you could even pass the data itself directly in the URL (depending on how much there is, of course, as a URL that runs to 1000s of characters is going to have compatibility probs).
Doable, but you may need some developer assistance on this one depending on your outcome: since you're using another platform to develop them, you have a few options. If the PDF is built in another platform that's connected to your CRM or similar (thinking something along the lines of Conga Composer), you could always just pass the path as a field (which would be the most straightforward). If there's a way from the PDF generator to dynamically retrieve the PDF based on identifying information such as customer/record ID, then you can just create a dynamic URL that links to the PDF generator output itself.
There are other courses of action you could take, but that's all dependent on what you're using for generating the PDFs today.