Files (such as PDFs, graphic and word processing files, spreadsheets and other formats) can be uploaded to references in EndNote.
You need to select the reference in your EndNote library, then use:
Method 1
From the References menu, select File Attachments, then Attach File
In the dialog box, select the file that you wish to attach to your reference, then click Open
Click on the Close button and then click on Save
Method 2
Click on the reference, and click on Attach File, locate the file to attach, then click on Open
The file will now be attached to the record / reference.
Click on the Close button and then click on Save