I have an odd smoothing issue with Preview in MacOS Sierra 10.12.6 on my retina MBP. Every right-hand (odd-numbered) page is very blurry, almost unreadable, while the left hand pages are somewhat blurry, but not quite as badly so (see screen capture below).
This happened suddenly, in the middle of a work session, there were no problems just moments before the issue suddenly occurred. I do not see similar blurriness on other viewers (Acrobat, Skim). The blur occurs both on the built-in retina screen and on my 1920x1200 monitor.
I decided to turn off font smoothing, but that option is now gone from the Settings window (when did this happen?)
What can be causing this weird behaviour?
Update: The smoothing issue persisted through several reboots, but has now disappeared.