You should have been given the dog's registration papers when you got it. You fill the papers out and send them in to the registry that the dog's parents are registered with. If you got the dog as a pup without papers you have to ask the breeder for them or the breeder can get duplicates for you. If by pedigree you mean you want to know more than just your dog's parents and grandparents you can order the pedigree from the registry. If it is UKC go to
http://www.ukcdogs.com/RegistrationFees.htm for all the information you'll need. This link will also give information and the form to single register your dog if you can't get the papers from the breeder. I'm not sure about how other registries work.
