You can attach files to the references in your EndNote library. There are two ways to do this.
1. Attach from the reference Summary (EndNote 20) or PDF (EndNote 21) tab in the right-hand window in EndNote
2. Attach using the References tab:
EndNote Click is a free browser plugin that helps you access PDFs by connecting to the Library's journal subscriptions and open access content. It works primarily with Google Scholar, and shows allows you to select multiple pdfs at a time and download them, along with their EndNote references.
EndNote Click is available for Chrome, Firefox, Edge, and Opera users. Use the link below to add an extension to your web browser.
Note:
Use File > Import or File > Import Folder to add PDFs to your library.
EndNote looks through the first two pages of the PDF for a DOI number that it can use to populate the reference. If the PDF matches a reference already in your library (and has appropriate metadata) EndNote will attach it to the existing reference.
You can set up auto import from a folder, but this feature will only become active on any new PDF's that are then added to that folder. Existing PDF's will not move across in this way and will have to be imported manually.