Interacting efficiently and comfortably with Augmented Reality (AR) headsets remains a major issue. We investigate the concept of mid-air pads as an alternative to gaze or direct hand input to control a cursor in windows anchored in the environment. ARPads allow users to control the cursor displayed in the headset screen through movements on a mid-air plane, which is not spatially aligned with the headset screen. We investigate a design space for ARPads, which takes into account the position of the pad relative to the user's body, and the orientation of the pad relative to that of the headset screen. Our study suggests that 1) indirect input can achieve the same performance as direct input while causing less fatigue than hand raycast, 2) an ARPad should be attached to the wrist or waist rather than to the thigh, and 3) the ARPad and the screen should have the same orientation.