Evangelicals are very suspicious of "those extra books" that Catholics have in their Bible, and often make the accusation that Catholics "added them to the Bible". Evangelicals are confident that they are using the true, original Bible. These claims, however, simply do not stand up to historical facts.
In the first three centuries of the Church, there was no total consensus as to what books should be in the Bible. Few people doubted the canonicity of the four gospels and parts of the OT like the Pentateuch. But regarding other parts of the Old Testament or the rest of the New Testament there was much dispute.
Origin accepted what's today called the Catholic canon, but minus James, 2nd Peter, 2nd John, and 3rd John, and plus the Shepherd of Hermas.
Athanasius compiled a list of 66 books he considered to canonical in A.D. 367. Since his Old Testament, like Protestants today, had 39 books, Protestants often cite his list as evidence that the Protestant canon existed in the early the Church. It is true that Athanasius' Old Testament indeed had 39 books, but not the same books as Protestants. He rejected Esther and included Baruch.
Books whose inspired status (or the lack thereof) was disputed at one point or another in the early Church include: Esther, Hebrews, James, 2nd Peter, 2nd John, 3rd John, Revelation, Tobit, Judith, Wisdom, Sirach (or Ecclesiasticus), Baruch, 1 Maccabees, 2 Maccabees, Shepherd of Hermas, 1st Clement, and the Didache.
So how was the canon eventually settled?
Around 383, Pope Damascus I commissioned Jerome to make what we now call the Vulgate translation of the Bible in Latin. The canon he instructed Jerome to translate was the same as the Catholic canon today.
In 393, the Synod of Hippo, a local council of north African bishops led by St. Augustine, affirmed a canon list that's the same as the Catholic canon today. This list was reaffirmed at the local councils of Carthage in 397 and 419.
In other words, the question was eventually settled by the Church authorities - the same way the questions were settled regarding the Trinity and the person of Christ.
But where was the Protestant canon of Scriptures? Not a single person or group in the early Church believed the Biblical canon to be what is now the Protestant canon. The Protestant canon, though many evangelicals believe it to be the original canon, did not exist yet and wouldn't for a long time.
For the next 1000 years in the West*, all Bibles were comprised of the Catholic canon. Whether the book was Genesis or Tobit, it was revered as Scripture, read in church, and quoted as an authority.
It wasn't until the 16th century that we finally find the Protestant canon, when the Reformers chose to remove books from the Bibles that everyone already used.
Catholics have a bigger Bible than evangelicals. But this is because Protestants removed books from the Bible, not because Catholics added "extra books".
*I say "in the West" because some groups in the East continued to dispute the book of Revelation, as well as accept a few books that Catholics reject. In any case, they don't lend any support to the canon used by evangelicals, which is the focus on this post.