There's Skim, quite popular among academics:
http://skim-app.sourceforge.net/
I've been using it for years and it's my preferred app, though it stores annotations in it's own way rather than to the PDF. They might be doing that since using OS X's built-in methods to edit a PDF might not have been reliable over the years and still might not be. I've tried most PDF apps, and for reading have stuck with Skim. There are others plus editors though I can't remember them at the moment. Another recent entry, commercial, decent and has tabs, though since it is fairly new, it isn't as rich as I'd like, is Readdle PDF Expert.
https://pdfexpert.com/