Importing pdf attachment from a reference manager?

This may be explained somewhere, but I could not find out where. I am trying to import a pdf from my reference manager (currently trying out Bookends) and I cannot find out how to import it into my Scrivener Reference files. Is there a way to do this?
Thanks,
Hilary

Hou should post this question in Technical Support, not in here. This part of the forum is for describing how you use Scrivener.

Thanks, sorry!