To the right of the preview tabs, there is a paperclip icon.
Click that to browse for and attach a PDF document to the current reference.
After attaching a PDF, click on a different reference in the list to indicate to EndNote that you have finished attaching, and approve saving the change (the attachment).
The PDF document can be annotated with highlighting, strikethrough, underlining, and "sticky notes". The PDF text will also become available for searching in EndNote.
To read and annotate a PDF document, click the Open icon.
To close the PDF, click the Close icon.