I upgraded to High Sierra a few days ago. Running a 2017 iMac (18,3). Today I have had trouble with Preview stalling just about every time I use it. Just now all my printers disappeared so I cannot print. When I go into System Preferences/Printers & Scanners, nothing happens when I click on the "+" sign. I have restarted several times. In activity monitor CPU Pressure is running under 15%, with System between 5% and 10% -- Memory is using less than 5GB of 16GB. Any ideas? --- Post Merged, Jan 3, 2018 --- Activity monitor showed that System Preferences was not responding for a brief time, but it no longer in red now. It also shows 23 recent hangs.