Yes, this is possible. Please see the images below

• Double-click on the citation containing the PDF in question. If you already have a PDF attached to your citation, you should be able to access it by clicking on the attached PDF (then click on Open) at the top of the reference entry - double click on the PDF to open (see image 'Endnote _20_find_PDF').
• To Highlight, add Sticky Notes (you can also underline, strikethrough text) click the Markup/Annotation button in the ribbon at the top of the PDF screen. Then, you just have to select the text that needs to be annotated in the PDF (see image 'Endnote _20_annotate_PDF').
• You can see that there is a Search PDF option (magnifying glass icon), at the top left of the PDF screen, which allows you to search in the PDF text as well.