So you are saying they were "adding to the Word" by putting these writings together? They were sinning by putting this library of inspired books together??<quoted text>
First of all, I wouldn't look at as violating scripture per se.
They way you're violating scripture however, is putting a false label on it.(Bible alone. Sola scripture)
Jesus never instructed anyone to put together a Christian bible. His Apostles never instructed anyone to put together a Christian Bible. No one they ordained instructed anyone to put together a Christian Bible.
The New Testament happened as a result of Catholic tradition and hierarchy.
If you are sinning, it would be because you're telling people that everything about Christianity is only found in the books the Church declared as canon. And you'd be sinning by manipulating those very words into a context that it was not written.
Please feel free to correct me on any contextual issues. If I'm wrong I want to know I'm wrong. I don't want to blindly follow men telling me what I should believe!