The Pan tool can be accessed in the toolbar on the bottom right of the screen, regardless of mode. When this tool is selected you can dag the screen around when you hold down your mouse while moving it.
There is not much more to it than that! But because you need it very often and don't want to constantly switch between the select and pan tools, PlanarAlly also binds the middle mouse button as a direct pan tool regardless of which tool you actually have active.
This results in me actually never using the pan tool as the active tool bar tool, unless I'm on a touchpad.