Post Mendeley shutdown, zotero has been an awesome replacement (while not being controlled by Elsevier). Given the amount of PDF's that I see during researchy times in my life, it's been an absolute godsend. Highly reccommend!
Zotero is the best. However, if your brain is highly tuned to use Mendeley Desktop, note that they backed down on killing it, they just won't add new features (where that leaves security updates I'm not sure).
