It wasn't so much editing as at the time the Council was formed all those books were known amongst the various Churches. Historically, the different Churches had various books that were used in worship. The Council attempted to find the common ground between all the Churches at the time, i.e. it was an attempt to determine what "mainstream" Christianity was based on how the Church had evolved over the course of 300 years.
Now, I'm not sure when the various dead sea scrolls, the gnostic gospels, etc. were lost in antiquity (and subsequently found), but I can assure you that with this 'editing' of various books out of the (New American) Bible (not the KJV, as Luther edited books that did not appeal to his particular world view), that the early Church was only attempting to find consensus amongst all the factions.
The Dead Sea Scrolls were found in the decade after WW-II and dated by secular archeologists to a couple hundred years before Christ. There significance is they said the same thing as the Bible on your grandma's coffee table. No changes in over 2000 years!
So this puts to rest the idea that Scriptures must have been corrupted over time "because that's how humans always screw up". Clearly that didn't happen with the Bible.