Milk, whether in liquid form or dry form, does not have a material effect on a pizza dough. It adds some nutrition in the form of calcium and some minerals, some protein, and a small amount of fat, but the main use of milk is to use the lactose sugar to provide more color in the crust. For a more detailed discussion of the role of milk in pizza doughs, see the PMQ Think Tank thread at http://thinktank.pmq.com/viewtopic.php?p=2027&sid=86e6354d5450988fdbc51465f5d25f22#2027.
See also Reply 6 at http://www.pizzamaking.com/forum/index.php?topic=3257.msg27655#msg27655
As best I can tell from some prior research, PH did not use nonfat milk by itself in its pan doughs. I believe that they used a dairy blend comprising whey, nonfat milk and buttermilk. If that blend appeals to you, you can buy a 50-lb. bag of it at Dutch Valley, at http://www.dutchvalleyfoods.com/food/ItemDetail.aspx/ItemID/129fb46d-3f5f-43a0-8aef-39f33e4d8a70.
Also, as you will see from http://www.pizzahut.com/Files/PDF/PIZZA%20HUT%20INGREDIENT%20STATEMENTS%20September%202008.pdf,
Pizza Hut is still using whey for its pan doughs but no dry milk or buttermilk. However, it is possible that PH is still using dry milk and buttermilk in countries outside of the U.S. where they still make fresh dough. Most of the doughs used in the U.S. are delivered frozen to their stores. That accounts for why their doughs contain so many chemicals and additives with strange sounding names.
I am quite certain that the NIDO (Nestle) brand of dry milk powder is a dried form of whole milk. It is often found in Hispanic supermarkets or in Hispanic sections of supermarkets (which is where I found it).
EDIT (4/20/13): For the Wayback Machine link to the above Pizza Hut pdf document, see http://web.archive.org/web/20100602083641/http://www.pizzahut.com/Files/PDF/PIZZA%20HUT%20INGREDIENT%20STATEMENTS%20September%202008.pdf