Obertan will be sidelined for up to five months after suffering a torn thigh muscle in the first half of last Saturday's 1-0 Premier League win over Liverpool.
Aarons replaced the Frenchman in the victory over Brendan Rodgers' side and Newcastle boss Pardew is in no doubt the 18-year-old, who recently returned following a hamstring injury, can soften the blow of losing the former Manchester United winger.
"Luckily Aarons has returned from injury at a good time for us," Pardew is quoted as saying in the Shields Gazette.
"We wouldn't have had the same impact [against Liverpool], I don't think, without his pace if we had lost Gabby
"We have lost Gabby but gained him, and it becomes one for one, really.
"We still carried the threat [in the Liverpool game], which is a fantastic tribute to Aarons, because he really hasn't trained much.
"To offer us the same threat as Gabby, in the form he's in, was great for him. It is a blow to us, make no mistake."
Resurgent Newcastle travel to West Brom in the Premier League on Sunday eyeing a fifth consecutive victory.
