How do you house train a paper trained dog?

The older the dog is the more difficult it will be but it is not impossible. Take your dog outside and walk him. Be consistent with this and commit to the time required. They will eventually have to go and when they do lavish praise on them such as "good dog". If you do this consistently they will prefer going outside and the paper habit will be broken. Remember that all Dog Training is essentially behavior modification and you must train them into the preferred habit. I hope this helps.