The club announced Monday that it had acquired Tulio Etchemaite, the second Argentine forward added to its roster in a week.
The 25-year-old Etchemaite began his career at River Plate in 2007, moving to Socio Aguila in Mexico and CD Moron in Argentina before playing last at Aragua FC in Venezuela.
He joins 36-year-old Pais, who was signed on a free transfer on September 10. Herediano is Pais' fourth Costa Rican club in five years, having played for Perez Zeledon, Cartagines and most recently San Carlos.
He scored six goals in 23 games last season for San Carlos, a year after he had 13 in 31 games for Cartagines.
Herediano has won both of its Champions League games, beating Real Salt Lake and Tauro by identical 1-0 scores. It will next play Tauro at home on September 25.