You can pan (or scroll) around the worksheet by holding down a finger and dragging the screen, in just the same way that you scroll through your email, except the panning works in two directions. To zoom in to an area, pinch together your thumb and forefinger on the area of the screen that you wish to zoom into and then expand your pinch to change the zoom level. Do exactly the reverse to zoom out. This is exactly the same process that you use for zooming in and out using Safari on the iPhone.
