
The first thing you should ask is WHY this person is selling the puppy on rather than handing it back to the breeder -if the puppy came from a responsible breeder then that breeder would agree to have the pup back at any time for any reason, whether it was after ten days, ten weeks or ten years. So that would worry me a bit. Good breeders want to know where their dogs are, keep in touch with the buyers for the life of the dog, and be there for any help or advice. If the breeder of this dog is a good, responsible one, then they will be upset that they have not been given the chance to select the new home themselves. Good breeders ask a LOT of questions of potential buyers to ensure they get the best possible homes. If the breeder doesn't care, then you as a novice owner will not have anybody to turn to should you need any help. A good breeder will always be there for any problems you may have, be it with training, general care, health or whatever.
Secondly, unless you intend to show, far more important than pedigree or registration certificate is proof of the parents having been health tested with good results. It's not my breed so I am not familiar with what tests you should ensure the parents have passed, but I do know there are several that all Staffords should have done before being bred from, to ensure they don't pass on problems to their pups. All pups are usually healthy, it's a few years down the line that matters. You should be given copies of health test certificates.
A pedigree can take any shape or form, the breeder usually prints one out with their own computer these days. You should however have the KC registration certificate which should be signed at the back by the present owner (or breeder if the first owner never transferred the pup into their name) and then you can just follow the instructions given on the form on how to transfer. This can be done either in the post or online. Make sure it is a Kennel Club registration certificate -there are other registries which basically do nothing but take people's money and the certificates are not worth the paper they are printed on.
If the pup is vaccinated you should be given a vet's vaccination card -normally this would have the vet surgery's name and address printed on it, the pup's details, and dates the vaccines were given plus what brand of vaccine -it should be two times. Batch numbers should be noted down and there should be a vet's signature.
Flea treatment is something many of us would only carry out if the dog HAD fleas -not as a preventative, and there are no certificates to show whether it has been done or not.