I guess it all depends on what the problem is regarding the paperwork. Did he buy the dog with paperwork?, did he buy the dog from someone other than the owner?, can not get a Biescheinigung? How long has he had the dog? Did he import the dog already bred? I waited a year for papers on a puppy imported from Belgium. Female I imported from the Czech Republic, already bred, I had the papers before the puppies were born. Just imported a Czech female, and although just received all the paperwork, it wasn't signed off and stamped by the CMKU (Czech Kennel Club) so I have to send the paperwork back to get everything corrected and in the proper sequence, before I can submit to AKC. There are legit reasons why the paperwork takes a longer time. Sometimes they just don't get in a hurry over in Europe, other times it's just a snafu.
I guess in your instance, you need to decide how you feel about the situation. What are you wanting to do with the pup. Do you feel comfortable waiting on the paperwork, as it could take some time? You will have to make that decision and go with your gut. The breeder is discounting the pup to about half price, but again, depending on what your purpose is for the pup, that may help you make your decision.