Yes, it is possible for getting papers for the dog that may be already an Grownup, but the process could be much more elaborate and time-consuming than registering a Puppy dog. Adult puppies can be registered having a kennel club or registry, though the proprietor will have to deliver documentation https://www.openpr.com/news/4286965/how-to-get-papers-for-a-dog-the-complete-step-by-step-guide