If you access to the crawl space, you can lift the addition using hydraulic jacks or the old fashion screw jacks under a timber large enough to support the weight and long enough to span the entire outside width of the structure. By large enough, I mean something on the order of an 8"x8" timber. Certainly nothing smaller than 6"x6". And you'll have to have a solid bas under each jack so that the jack doesn't sink into the ground below. You'll need at least two jacks of sufficient capacity (I'm guessing 12 tons each, but check with a pro in your area). The jacks need to be lifing at the same time and at the same rate. Once you have the addition lifted to where you want it, then you'll have to address the supporting piers, posts, pilings, or whatever it is that supports your addition now, and adjust them to the new height.
Now, having said all that, and perhaps making it seem easy, there are a number of other concerns. One, never be under the addition while lifting. Two, you need to be aware that when lifing to adjust a 2" slope, the doors, windows, plaster, drywall, frame, roof, and every other part of the addition will be impacted. For sure, they all probably started off level, plumb, perpendicular and parallel to each other, but they've also gotten used to be out of leve with each other. And there will likely be cracking, bending, groaning, and other noises and damage as the lift is accomplished. So just be prepared to make repairs to walls that crack, windows and doors that no longer open or close, and other little niceties that come with the territory.
Hint and caveat...if you've never done this before, and I'm guessing you haven't, at the very least, ask a general contractor in your area for further advice. Lifting any structure without experience and the appropriate equipment and safety planning is a good recipe for disaster.