Don't have Highlights installed? Get it from the App Store.
Highlights can be integrated with the popular reference management app Bookends. This allows for seamless reading and reference lookups in Highlights without web searches or downloading the same article twice.
How do I enable it?
Open Preferences, go to the Advanced-pane:
Set the Reference Manager to Bookends:
For the best experience you should set Bookends to open PDFs in Highlights. As Bookends does not have a default reader preference, you will have to do this at the system level. Keep in mind that this will make Highlights as the default application for opening all PDFs on your Mac.
To do this, right-click on any PDF file in the Finder and select Get Info from the menu. In the Get Info panel find the Open with-section and select Highlights from the drop down menu. Click the Change all… button below. A system dialog appears, confirm the change by clicking Continue.
How does it work?
When enabled, the header links in notes with fetched metadata will redirect to Bookends:
Similarly, any citations you lookup will get a Bookends-link:
If Bookends has the PDF for the specific reference in its library it will open it:
If Highlights is set as the default reader, it will bounce back to Highlights and open it there directly.
If Bookends does not have the PDF, it will open the link in the built-in browser so you can download it: