The first place to check on a KitchenAid dishwasher for leaks is at the door seal. Open the door and look for any food bits or other debris that may have stuck to the edges of the seal or lodged between the seal and the door. If you see anything, pull the seal away from the door slightly and remove the debris. Also check for rips or holes in the seal. If there are no visible marks, run your hand along the perimeter of the seal to ensure it does not feel loose.
If the seal on your KitchenAid dishwasher has holes, rips or feels loose, it should be replaced. You can order a replacement seal for your model of dishwasher from KitchenAid's website then replace it by following the directions and using the hardware provided. If the dishwasher is still under warranty, you can have the seal replaced by an authorized repair technician for free; replacing the seal yourself can void the warranty.
If you find no issues with the door seal on your KitchenAid dishwasher or if you replace the seal and the unit still leaks, set a level on top of the appliance from front to back on one side. Move the level to the other side, if the bubble indicates that the dishwasher sits even on the first side, to ensure that the other side also sits even. Then lay the level along the front edge of the dishwasher to ensure that it sits even from side to side as well.
If your KitchenAid dishwasher sits uneven in any direction, adjust the legs on the unit by releasing the small pins at the side of each leg and moving it downward or upward in its shaft. Check the dishwasher again with the level, after adjusting, to make sure the unit sits even. If you cannot get the unit exactly level, it’s better for the dishwasher to sit slightly higher in the front to prevent leaking.