By Mark Lamport-Stokes
Pacquiao, 51-3-2 (38 knockouts), tipped the scales at 144.6 pounds in front of a jubilant crowd of about 1,000 at the fight venue -- the imposing, state-of-the-art Cowboys Stadium.
Mexican Margarito (38-6, 27 KOs) was right on the limit for the scheduled 12-round bout which will be fought at a contracted weight of 150 pounds.
"I have trained a lot and I think because of the training hard that's why my weight is what it is," Pacquiao told reporters after the televised weigh-in.
His trainer Freddie Roach said his fighter was simply coming in at his natural weight.
"He's in great shape," Roach added. "I gave him the green light to just take care of himself and he got out the protein shakes. That's what we wanted to come in at."
Although three-times world champion Margarito enjoys a significant height and reach advantage, Pacquiao is widely expected to beat his Mexican opponent.
The atmosphere was electric as the two fighters made their way on to a raised stage for Friday's weigh-in where Jerry Jones, owner of the Dallas Cowboys NFL team, was among those attending.
Shouts of "Manny, Manny, Manny" and "Mexico, Mexico, Mexico" resounded before the two boxers emerged, the ever-smiling Pacquiao wearing a white balaclava, a yellow shirt, blue jeans and a red tracksuit top.
Margarito, who wore sunglasses, a black tracksuit top and black boxing shorts, was booed by a large section of the crowd before he weighed in first, flanked on either side of the stage by three Dallas Cowboys cheerleaders.
The disgraced Mexican and his trainer Javier Capetillo were banned for a year after plaster-like bandage wraps were found in the fighter's gloves before the Mosley fight.
Margarito, dubbed the 'Tijuana Tornado', last fought in May when he beat Roberto Garcia in a WBC international light-middleweight bout in Mexico.
(Editing by Steve Ginsburg)