If you do this straight after it had come out of the smoker and was still hot, you could apply the smoke from the AMNPS without heat for up to 2 hours without a problem if it is going to be served and eaten straight away.
You have probably already allowed it cool though to pull, and it is already in the refrigerator. In this case you can re-smoke it just before serving. Place it spread out in an open tray in your smoker, with maybe a spray of apple juice for moisture, along with your AMNPS. Use the smoker to reheat the pulled pork until it has reached at least 165 F (74 C) before serving.
With either method food safety will not be an issue. Usually though when you reheat pulled pork you would do so with it covered in foil to retain moisture - so with the second method you need to make sure that it is not allowed to dry out.