To pan around the score you can make use of a mouse wheel, multitouch devices, such as Magic Mouse or Trackpad, or scroll bars.
Vertical scrolling of the score is performed by moving the mouse wheel up or down.
Horizontal scrolling of the score is performed by pressing Shift key and moving the mouse wheel up or down.
Scrolling can be performed by dragging the horizontal or vertical scroll bar. Scroll bars are hidden until you use another scrolling technique, such as moving the mouse wheel or the trackpad gesture.
When using a Magic Mouse you can pan the score by sliding one finger.
With the Magic Trackpad or built-in Multi-Touch trackpad, for panning around the score slide two fingers.