Yes, Pope Nicholas V wrote a papal bull in 1452 to Alfonso V of Portugal (and also authorized the same for Spain). In that writing it authorized Alfonso V to consign the pagans to "perpetual servitude." Pope Calixtus III renewed that bull and Pope Sixtus IV and Pope Leo X (in 1514) again renewed the bull. "We grant you by these present documents, with our Apostolic Authority, full and free permission to invade, search out, capture, and subjugate the Saracens and pagans and any other unbelievers and enemies of Christ wherever they may be, as well as their kingdoms, duchies, counties, principalities, and other property... and to reduce their persons into perpetual servitude." There was a movement against enslaving Christians, but no such qualms with regards to non-Christians and a lot of ambivalence towards non-Christians who converted to Catholicism.

To add on /u/pfeifits's answer, Pope Paul III wrote a bull in 1537 in which he forbade "unjust kinds of enslavement" relating to the indigenous peoples of the Americas (called Indians of the West and the South) and all other people. Paul characterized enslavers as allies of the devil and declared attempts to justify such slavery "null and void."

Accompanying the bull was another document, Pastorale Officium, which attached a latae sententiae excommunication remittable only by the pope himself for those who attempted to enslave the Indians or steal their goods.

However, it was annulled the following year due to a dispute with the Spanish crown.