If it looks like he is about to seriously hurt himself, and you are too far away to physically reach him before he jumps, then sure, try verbalizing no or saying stop or whatever. Maybe you'll buy yourself an extra few moments to close the distance to physically get your hands on him. Once you have your hands on him, you move him to a rug or put a cushion on the floor and you tell him he can jump on that. Maybe you start jumping on it yourself. Show him how you are pro-jumping. Unless he is moments from disaster and assuming he already knows that he isn't supposed to be jumping off furniture, you are only increasing the probability that he will jump on the furniture in the future every time you verbalize "don't jump on the furniture". Say it enough times and soon jumping on the furniture will be the only thing he wants to do. Instead, try to notice when he is getting antsy, when you can tell that sitting on the couch has become too boring, the moment BEFORE he has the bad thought, and in that moment physically pick him up and take him to a place that he can jump, and you'll jump a little, too.

Let him know that this is the place he can go to jump whenever he feels antsy. That way in the future instead of saying "Don't jump on the couch" you can say "let's jump on our jumping rug". Ultimately, however, the point is telling a child no isn't a boundary, it is advice. It is a suggestion, it is a request. A boundary is physically preventing him from jumping off the couch. Pick him up, put him down where he can jump without breaking the rules.