Ronaldo, 29, is the hot favourite to land the award for the third time in his career, having also won it in 2008, when it is presented at a gala dinner in Zurich on Jan. 12.
Pepe has told national newspaper A Bola that "it would be a scandal if they did not give the Ballon d'Or to Cristiano Ronaldo this year."
The defender was asked: "Can anyone admit that Ronaldo is not going to be the winner of the trophy?"
The centre-back was strong in his reply, saying: "If any other player wins, they should be ashamed given what Cristiano has been doing, beating lots of records, scoring 17 goals in the Champions League last season, these things are almost impossible."
Pepe also highlights the glut of goals Ronaldo has scored in such a short space of time this season: "In three months he has scored 23 goals. What else does he need to do? He is the best player in history and I repeat, it would be a scandal and a shame if they did not give him the Ballon d'Or."
On Dec. 1, FIFA will release the three-man shortlist for the award at this year's gala, organised by FIFA and France Football.