You can do it like deaddog told you, or you can go like Messiah stated.
If pitch shift solves your problem , look no further, but if you feel the neeed for extra editing , go for the sound editing way. You can pitch shift, add some EQ, and maybe add some reverb if you need to simulate some kind of room or any kind of environment (well, that takes some practice in order to achieve realistic results). It all depends on what you're after.
Hope this helped you.