@dlordmills Just checking if you misread, perhaps? When Klaas says CTRL/Cmd+F, it means Ctrl+F OR Cmd+F. Not Ctrl+Cmd+F.
Ctrl+Cmd+F is fullscreen.
on MacOS, Cmd+F and I assume on Windows it is Ctrl+F makes a little search text field for searching within your document. But it seems that this only works in Edit Mode, not in Preview Mode.