Hi,
the PWM tutorial (http://www.arduino.cc/en/Tutorial/PWM) does not reflect the extended capabilities and the special properties of the Due. I suggest to mention the function analogWriteResolution() and the reduced output amplitude of 3.3 V.
Another interesting topic is the PWM frequency - it is covered in the tutorial http://www.arduino.cc/en/Tutorial/SecretsOfArduinoPWM. I suggest to place a link to this informative tutorial in http://www.arduino.cc/en/Tutorial/PWM. But again: The Due is not mentioned there either. How to program the timers of the Due? What timers are already occupied by the Due/SAM runtime system?