check the hinges. there should be a star key, an allen key or an ordinary screw for adjustment. if you cant find it check for cover plates. make sure you adjust all hinges eavenly. failing this check the rubber seal underneath the door hasnt come loose. this is quita a common problem
aaron, December 2011
I have the same problem myself. I have yet to try but i think there are adjusters on the hinges
les, December 2011
edit
I can answer this question...
how do I adjust my upvc balcony door as it keeps sticking?