I have rented the same apartment for 6 years in PA. I wish to have my carpets profesionaly cleaned. They have not been cleaned since I moved in or before hand. Who should pay the bill, me or the landlord?

Usually the tenant is responsible for cleaning the carpet... unless of course, the landlord made them dirty.

Unless it is in your lease for them to clean them, you are responsible, as you would be to clean them before you moved out.

Usually it's the tenant's responsibility, especially if the carpets are dirty beyond "normal wear and tear". However, if you've been a good tenant, and if you have a smart landlord, then the landlord will want to keep you happy. Why not ask the landlord to pay for it? If they say no, ask if they'll split the cost with you. It can't hurt to ask.