How do you adjust butt hinges on a uPVC door?

You can use the adjustment slots. Check your owner’s manual to see if your uPVC door has 1 or more adjustment slots, which are usually hexagonal in shape, in its hinges. If it does, you may need to lift off a protective cap on each hinge to expose the adjustment slots. With some door models, you may need to first open the door and slightly loosen the screws that hold the each hinge to the door frame in order to remove the adjustment slot caps. Then, use an Allen wrench that fits into the slot and turn it clockwise or counterclockwise depending on what kind of adjustment you're making. Start by making 1-2 full rotations, and keep track of how many rotations you make. Then, adjust the rest of your hinges with the same number of rotations to make an even adjustment. Open and close the door to see if it needs more adjustments. When you're finished, replace the protective caps if you had to remove them.