I use the mouse wheel button to scroll through documents. Sometimes I inadvertently "double-click" the mouse wheel button, and this brings up a box in the upper right-hand corner of the window. I don't know what to call it because I don't find a mention of it in the documentation. It looks like a thumbnail of the current page and allows the user to select the part of the page that is displayed by moving the box that corresponds to the page view area.
Is there any way to disable this behavior?
I don't see a way of disabling it from within Reader. Maybe in your mouse settings?