In some cases its not possible, for example there are no copies of the first version of the bible.
So how can we tell if any of subsequent versions are accurately transcribed?
That has always been my thought also. As kids we did this "whispering in ear game". The story changed immensely. So, using my common sense, I know that the Bible and the Koran can not be error free (even errors are due to happen when "God" whispers in prophets ears, unless prophet is also "God"). The weakest (least pure) link determines the final outcome.
But maybe errors are meant to be in Scriptures, otherwise it would be too easy. Indian Saints declare "You are God". So, when perfect wisdom would be in the Scriptures, one would be less motivated to look within, to realize "I am That (God)".
But after 2000 year an update would not be too much of a luxury, as people still kill each other over the Bible. Would be really great if Jesus came to the earth to highlight all the errors in the Bible that slipped in (and correct them). And when Jesus updates to Bible2 then afterwards it will be quite error-free since we have digital backups
(when they don't start with EMP or so)