In the same year he confirmed Trent's decrees, 1564, Pius IV promulgated two documents that shaped Catholic practice for centuries afterward. The Index of Prohibited Books, drawn up at the council, listed works Catholics were forbidden to read or possess, formalizing a mechanism of censorship the church had used informally for decades into a standing institutional apparatus that would continue, revised repeatedly, into the twentieth century.
The Tridentine Profession of Faith, promulgated the same year, was an oath of orthodoxy required of bishops, beneficed clergy, university teachers and converts received into the Roman church, a practical enforcement mechanism that made adherence to Trent's doctrinal conclusions a condition of holding office or teaching rather than a matter of private belief. Pius IV is credited with enacting these texts rather than authoring their content, since both were substantially the council's own work; his role was to give them the force that only papal promulgation could supply.
Together the two documents illustrate how Trent's authority reached the church's daily life: not only through doctrine defined in council sessions, but through an index that controlled what could be read and an oath that controlled who could teach, both dated to the final year of Pius IV's central achievement.