How do you get dog pee smell out of leather?

The correct starting point is to use an enzyme based pet urine odor eliminator. There are many brands available at your local pet store or vet. Make sure you test in an non obvious area to ensure that the odor eliminator will not have an adverse effect on your leather. If the odor has seeped into the internals of a seat cushion, then I advise replacement of the seat cushion. If it seeped into the frame, then open the dust cover (cloth under the piece) and apply enzyme based odor eliminator on effected components. It may require multiple doses of the odor eliminator. Finally, if the odor is persistent the place the target piece in an ozone chamber. Your local disaster relief company (flood and fire) should have an ozone chamber. For more information on urine and leather go to: http://www.diyleathersolutions.com/petdamage.html