I have an old international 3 board plough. On it. one of the hitch pins is mounted eccentrically, so that you can raise or lower one side by loosening the bolt, rotating it, and retighten. I've never done this as it's rusted solid.
My tractor instead has adjustible lift arms, so I can fix it that way.
An additional ad-hoc adjustment is tire pressure. You can get a couple inches either way by playing games with the tire pressure.
Also: The first row is always a bit wonky unless you readjust for the first row, and then adjust back. In normal operation, one front wheel is in the trough adjacent left by the previous strip. This means that on the second and subsequent rows, you are 4-6 inches lower on one side. On a long day, this is tough enough on lower back, that I end up either bringing a cushion with me, or wadding up my jacket into a wedge shape to sit on.