The first major project undertaken by Gutenburg was printing the Bible. The Bible continued to be the book most frequently printed -- it is still, in terms of the numbers of copies printed, the single best selling book in the history of the world. The Roman Catholic Church was not particularly enthusiastic over the wide dissemination of the Bible. In early modern Roman Catholicism, the laity were not encouraged to read the Bible. Instead, excerpts from the Bible were read in Latin (which was only understood by a small elite) as part of the Mass and then explained in the vernacular by the priest. Thus the Bible was only made available as mediated by the church hierarchy and within the context of the way the Roman church interpreted it.
Protestants developed the sola scriptura (salvation can be achieved by reading and following Scripture on one's own) doctrine, and were active in translating the Bible into vernaculars, using the technology of print to distribute it widely, and encouraging people to read it for themselves. This was viewed as heretical by the Roman Catholic church because it encouraged "private judgement." It was not until Vatican II in the 1950s that the Roman Catholic mass began to be said in the vernacular.
Thus the Roman Church disapproved of printing the Bible in the vernacular and, in some cases, in the Greek (e.g. I John 5.7 controversy) and responded to printing other books depending on the books -- they approved of printing the Church Fathers and many ancient works, and disapproved of works they thought heretical.