Editing the XML file worked for me too. Thanks for this workaround.
Adobe obviously needs to fix this usability issue- it's super annoying to have toolbars and dialogs with NO WAY TO TURN THEM OFF OR HIDE THEM. There is also no way to get the Reader DC to go into read-mode automatically. I guess I'll be hitting Ctrl-H a lot.
The only reason I'm using Adobe is because when opening large GeoPDF map files, it's the only reader with fast enough performance.