It should do.
The metal body panels on the mk6 GTI 5 door should be the same as those on any other mk6 5 door Golf, and a 3 door mk6 GTI shares the same body panels with any other 3 door mk6 Golf (plastic bumpers will be different on certain models). Therefore a replacement door doesn’t necessarily need to come from a GTD; one from a GT, R, Match, SE or S should also fit. If you’ve got a 5 door, the replacement door will need to come from a 5 door. Similarly, if you’ve got a 3 door you’ll need a door from a 3 door as the doors on a 3 door are longer than the front doors on a 5 door model. You’ll probably need to use your existing door card too, and your existing door mirror; if your car has the dipping kerbside mirror function on the nearside door mirror, if the replacement door comes with mirror, it might not have the dipping function.
The doors from the mk6 estate won’t fit though, as the mk6 estate is effectively a mk5 estate body (including mk5 estate doors) with mk6 style front end.
Edit: the cabriolet doors won’t fit the 3/5 door hatchback either as they’re frameless.
