Preview is part of the OS, so you'd have to use recovery to reinstall the entire OS - it will not erase your files; however, it is always best to have a backup first.
Tip: The 64-bit version is installed by default unless Office detects you already have a 32-bit version of Office (or a stand-alone Office app such as Project or Visio) installed.In this case, the 32-bit version of Office will be installed instead. To change from a 32-bit version to a 64-bit version or vice versa, you need to uninstall Office first (including any stand-alone Office apps you. Firefox Preview Nightly For Mac – Download on Windows And PC Latest Version By appformac One of the powerful and strongest apps on the app store is Firefox Preview Nightly for Mac which is holding the average rating of Total rating isn’t available.
Can you check two things: open Activity Monitor (in Applications > Utilities) and if Preview is running, kill the process. And, go to your user library > Preferences and find these:
Move them to the trash (do not empty yet). Restart Mac and see if the problem persists. The prefs files will be regenerating themselves. If something does not, simply move them back from the trash.