I grow a lot of Jade plants - they really do best in extremely bright filtered sun and staying on the dry side - the more sun the more compact a plant. If that was my plant and I wanted to rejuvenate it I'd start cutting off branches close to the main stem. I wouldn't do it all at once. I'd make one cut and wait until the cut calluses over and new growth starts to appear. Once new growth appeared, I'd cut another branch off and do the same thing over and over until all the long stems are gone. You can also root what you cut off for 'insurance'. Once it's completely pruned and growing well, I'd take it out of it's pot and with a sharp bread knife, cut away a third of the soil on all sides and bottom then repot it into a smaller pot. Jade roots seem to like hugs. The picture is showing where I'd make the cuts.
Keep in mind that it probably won't be until next year that the plant starts to look 'normal'.
