As a user i would like the ability to add attachments that I have already uploaded to Aha to my notebooks - just like almost any other view. Just re-use the "add to notebook" button in the attachment viewing modal window.
Max - what are you hoping create as a PDF? Did you know that you can generate your Notebooks as a PDF? Please see the screenshot for details on generating a PDF, as well as a way to attach files directly to your notebooks.
Ok, on further digging, you can actually click on the attachments in a Release in a notebook. So the addition would only be needed for PDF output.
It looks like you can do this for attachments in Features and Requirements, but not for attachments up at the Launch level. So that is where to add the "Add to notebook" functionality.