The idea that the 7 books were added at the Council of Trent is one of the five most common myths that surround them.
St. Jerome. In his later years did indeed accept the Deuter-ocanonical books of the Bible. In fact, he wound up strenuously defending their status as inspired Scripture, writing, "What sin have I committed if I followed the judgment of the churches? But he who brings charges against me for relating the objections that the Hebrews are wont to raise against the story of Susanna, the Son of the Three Children, and the story of Bel and the Dragon, which are not found in the Hebrew volume (ie. canon), proves that he is just a foolish sycophant. For I wasn't relating my own personal views, but rather the remarks that they [the Jews] are wont to make against us"
I am not saying they were added at the Council of Trent, obviously. Otherwise there would have been no contention about them in the 16th century. The argument simply is they were not deemed canonical until the Council of Trent. It is obvious they were not deemed canonical prior to this, otherwise the church would not have needed to bring the subject up in the Council of Trent.