In most walks of life, mistakes in electronic documents get fixed when found. The fix generally involves just editing the original. No big deal.
However, this is not always the right thing to do. Legal documents for example are best thought of in book keeping terms. If a bookkeeper finds an error in a ledger he or she does not simply edit it. Rather, a new debit/credit is recorded to counter-balance the error but leave the integrity of the records intact.
Here is a good example from the US National Archives. "Fixing" an original - however broken, is a no no. Fixing a variant - with audit trail back to the original. Thats a different matter.