Pan and zoom
Pan, zoom, wheel, right button

The view zoomed right in on the snowy peak: dense rulers and the toolbar with the framing buttons

Pan the view

GestureWhat it does
Drag with the right buttonpans the view, with any tool active
Hold Space and dragpans the view, with any tool active
⌘ + wheelpans the view in the direction of the wheel (or trackpad)
A right-click without moving the mouse (within 4 pixels) opens the context menu; as soon as you move it becomes a pan.

Zoom in and out

GestureWhat it does
Wheelzooms in or out around the point under the pointer
⌘ 0Fit to view: the whole drawing in the window
⌘ 1Zoom 100%: one drawing pixel per screen pixel
⌘ ⌥ 0Zoom to selection: the selection in the window
fit selection / page to view buttonthe selection if there is one, otherwise the active page
Double-click on an empty area of a pagefits that page in the view and makes it active, without selecting it
Double-click on an empty area outside the pagesfits the whole drawing in the view

Zoom ranges from one thousandth to 160 times. If you turn the wheel while holding a mouse button, the view stays still.

While drawing

Pan and zoom also work in the middle of a gesture: in click-and-click mode you can place the first point, turn the wheel, pan the view, and place the second point elsewhere. See The two ways of every gesture.