This is one of the reasons we stay in business! Jumping teenage dogs whose owners let them jump all over them as tiny pups. It’s not too late to teach an old dog new tricks, but it is MUCH MORE DIFFICULT!
Remember, this is like teaching young kids to say “please & thank you”… it is very important to teach them manners but we spend 18 years reminding them until they hopefully grow into decent human beings. Your puppy will need plenty of “reminding” the first 1-2 years of his life 🙂 Also, just as with children, it’s better to be proactive about teaching them what you want, than to react angrily every time they don’t behave the “right way”. Punishment is often ineffective, timed wrong, or unfair because the puppy is really clueless about what you want instead.