Easier technic to preview a PSD on iOS: Open an additional view for your file (Window -> Arrange -> New Window) and place it one the side. Download the free tool 'LivePreview' http://www.zambetti.com/projects/liveview/ and place its window on top of your cloned Photoshop view. Open your iOS device, install the 'LivePreview' app and connect to your machine. Wolla - a live preview!