Originally Posted by Charles Kenyon

This setting is not saved or contained in documents. It is a Word setting.
Absent macros, opening a document will not turn the setting on (check it).

However, once it is on for a single document, it is on for all documents opened thereafter until changed back.

It can easily be turned on/off with a double-click at the top/bottom of a document page.

I am on a laptop with a touchpad which gives me stray mouse-clicks all the time. If you are using a touchpad, consider attaching a mouse and telling Windows that when a mouse is attached the touchpad should not respond.