If Word opens with reading pane view by default and you do not want to change it every time here is what you require to do:

If you would like to turn it off for existing session and go back to print layout or normal view then you can tick close on Reading Layout toolbar.

To avoid reading layout view from opening mechanically when you get a Word document go to Tools menu, tick Options, tick General tab, and then clear the Allow starting in Reading Layout check box.