Paço, 16, surfed for a total of 16.33 points, leaving Spanish surfer Carmen Lopez in second place with 7.53, and North American Barbie Pacheco in third, with 2.77.
The Portuguese surfer dominated the competition against her two opponents, achieving the four best waves in the final.
The teenager from Viana do Castelo, an athlete at the Surf Clube de Viana, had previously achieved a bronze medal on her debut at the World Championships in 2018, was crowned European champion the following year and has now won the title of world champion in her class.
After the victory, which took place at Pismo Beach, in the North American state of California, she said she wanted to be "an ambassador of parasurfing", trying to motivate more people to join the sport.
The president of the Portuguese Surfing Federation (FPS), João Aranha, highlighted the clubs' work for the growth of parasurfing in the country and praised Marta Paço as "the world's best parasurfing talent in this category".
Surfing made its debut in the program of the Olympic Games, in Tokyo2020, but it still doesn't feature in the Paralympic program.