Yes, it can be done to have papers to get a Pet dog which is now an adult, but the method can be far more elaborate and time-consuming than registering a Pup. Adult puppies is often registered which has a kennel club or registry, though the operator should give documentation https://www.openpr.com/news/4286965/how-to-get-papers-for-a-dog-the-complete-step-by-step-guide