Copy PDF attachment from one reference to another (within a library)

I have two citations in the same library, one with a PDF attachment of the paper, one (a more fully populated citation), created by importing an RIS file from the original data source (which currently does not have the PDF attached).

is it possible to paste the attachment from the one reference into the other within EN? Or will I have to add the original PDF to each and every reference? It’s a large library and set of associated PDFs so any thing streamline the process is a help.

 Thanks 

Not to my knowledge.  You are really wanting a merge references option, which has been asked for for years, without success.