Acrobat Reader now remembers the state of your Tools pane. If it was collapsed (or expanded) during the last launch, it remains collapsed (or expanded) when you launch again.
For more information please use the help article (https://helpx.adobe.com/in/acrobat/kb/disable-right-hand-pane-in-acrobat-reader.html)
I hope this will help
Let us know if you are referring to something else.
Regards
Amal