EndNote allows you to add PDFs, images or other files to your references.
In your EndNote library, select (click) the reference you would like to attach a file to
Select Attach File >select file > click on the Open button
Then click on Edit > Save
Finding Full Text
EndNote Desktop will search for the full-text PDFs, and automatically attach them to their corresponding references in your EndNote Desktop library. To find full text:
In your EndNote library select (click) the reference you would like to attach a file to
From the menu bar, select Reference > Find Full Text > Find Full Text