What docmanhatten said. The free bibles, or other religious works for that matter, given out online or wherever usually aren't all that. Poor quality, no annotation, etc. Good for simple purposes, but any in depth study will be stymied.
As for good versions for study/research/rebuttal/what-have-you purposes...check college books stores near the start of the term. Any classes on religion will tend to have good academic versions of religious texts. (Which is why my academic library includes a good bible, quran, bahgivad vita, upanashads, as well as commentary texts by the likes of Augustine and Aquinus. And all this from a heathen.) There are also some good ones online, but like most books, a physically thing is so much easier and nicer.