There is a free ePub on the iBookstore in the original Latin (also a paid one in English)
If you read anything by Newton, I would advise Opticks, by the way, to learn that, even for geniuses, it is all hard work to get there (TL;DR version: he did not order his lenses on the Internet and needed the sun (in England) for lots of his experiments)
It also is on http://books.google.nl/books/about/The_Mathematical_Principl..., but 'not yet available in your country' for me, so I don't know whether that is good.
There is a free ePub on the iBookstore in the original Latin (also a paid one in English)
If you read anything by Newton, I would advise Opticks, by the way, to learn that, even for geniuses, it is all hard work to get there (TL;DR version: he did not order his lenses on the Internet and needed the sun (in England) for lots of his experiments)