Jaw Shaving or Contouring Concerns

Is there a limit as to how much the jaw can be shaved? I would love my jaw to be drastically smaller and slimmer. What are the risks involved as well? Will there be possibilities of permanent face swelling, and would it result in difficulty in speaking and pronouncing? I've seen pictures of women's faces swelling up like balloons. I'm really afraid of that. More importantly will the process be very painful, especially when it comes to recovering?