Can the Church Change the Bible?

Practically speaking, no. The Church cannot alter the books it has received and declared canonical and inspired. Strictly speaking, the Church’s declaration of the canon of Sacred Scripture at the Council of Trent did not say that one could not hold that there are other inspired books than those declared as canonical, but only that the ones received as such are the only ones now received in the universal Church. These alone are read as Scripture in the Church and used in theological disputation.

So, for example, if authentic versions of lost letters of St. Paul were found (a thing practically impossible), we might have to examine their status with his other letters. But the Church has its own rule of faith, and most of the purported books of Scripture discovered later (such as the findings at Nag Hammadi in Egypt in the past century) have teachings that contradict the orthodox Faith.