In the same way that there is no original copy of the Bible, there is no original copy of the Koran. In some ways that is surprising, insofar as it is the work of one man and a few scribes, whereas the Bible is probably the work of hundreds. It was written over many years.
There seems little doubt that it was revised, edited, rewritten, re-revised many times during it's inception (otherwise why would such a (comparatively) short book have taken so long?