You can add a buy now button to a .pdf document.
If someone you know works with pdf files, you may want to have them assist you with this process.
Here is a reference video (accessed by searching google for "paypal button in pdf") that may help.
[HOW TO] Add a PayPal Button to PDF Document
Add a paypal button to a .pdf document by inserting an image object and overlaying that image with a link object.
Info from PayPal:
Putting a PayPal button on a PDF-based newsletter
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