Keyboard shortcut to turn off automatic highlighting in preview?
To turn it off, you have to go back to &quot;text selection mode&quot; but unfortunately, there's no keyboard short cut.   From the Tools menu, you would click on Text Selection to get out of the automatic highlight/underline/strikeout mode.

However, we can create one!
In System Preferences → Keyboard → App Shortcuts create a new shortcut by clicking the &quot;+&quot;.  Then, in the drop down, select &quot;Preview&quot; for the App, type the exact name of the menu title, in this case &quot;Text Selection&quot; and assign it a shortcut.  I used ⌘ Command^ ControlT to stay consistent with the other shortcuts.