This method is beneficial when you already have a reference's PDF saved on your PC or USB, or when the reference lacks a DOI. This approach is used for one reference at a time, not several references at the same time.
If you open up a citation that is already in EndNote by clicking on its title, you will find an attach files link about a third of the way down the page
- 📷 Attach files - that will allow you to upload your PDF.