Hehe, enthusiasm is contagious mouser!
@ -Huub- this works when Reader app is fullscreen in Win 8.1
CoordMode, Mouse, Screen
MouseGetPos, mx, my
if (A_ScreenHeight - my > 101 or mx > 101 )
A drawback is that it breaks click and drag in Reader (multi word text selection). But you can still do ctrl+click and drag to select text.