You can rotate objects by 90 degrees or by a custom angle.  For example you might rotate a component footprint to make it better fit your circuit layout.

alt To rotate an object 90 degrees:
  1. Select the object.
  2. Choose Edit | Rotate; or
    on the Property Bar click pcb-rotate-tool.
alt To rotate an object to a specific angle:
  1. Select the object.
  2. On the Property Bar in the Angle field enter the angle and press Enter.