How do I shift pitches on an Audio Files?

Import the audio track, select from menu Process-Transpose (make sure transpose audio box is checked), and specify the transpose key amount.

Edit : also select the entire clip first (or parts to be transposed).

I'd vote for Process > Transpose IF you don't demand real time processing. It uses an offline algorithm that sounds very good with modest amounts of strettching. Sometimes I record background vocals listening to the track a semitone down, and when it gets transposed back up, the vocals have a slightly brighter timbre that works well.