In Adobe Reader you can: https://helpx.adobe.com/acrobat/kb/disable-right-hand-pane-in-acrobat-reader.html

In Acrobat Pro this option is not available. Atm i work with dozens of pdfs wich i open multiple times and i have to close the Bookmark pane every time.

I tried lot of solutions (even edit registry key) and tried to install adobe rader but it says "...already installed" and opens Acrobat Pro :'(