The third seeded Russian looked on course for an early exit after losing the first set, but she hit back against her Spanish opponent.
Pavlyuchenkova eventually came through 5-7 6-2 6-3 after a titanic tussle that lasted two hours and 42 minutes in Seoul.
Russia got another one over on Spain as Vera Dushevina eased past Silvia Soler-Espinosa 6-4 6-1, while German sixth seed Julia Goerges was given few problems in a 6-3 7-5 win over Japan's Misaki Doi.
Ukrainian fifth seed Elina Svitolina was less fortunate as Lara Arruabarrena edged to a 7-5 2-6 6-4 triumph.
Home favourite Ye-Ra Lee cruised past Daria Gavrilova 6-4 6-1, Korean compatriot Sung-Hee Han crashed to a 6-0 7-6 (7/0) defeat against Romania's Alexandra Dulgheru and Virginie Razzano of France hammered Lourdes Dominguez Lino 6-1 6-1.