It DOES?
Yes, it does. Deuteronomy 13:1 says:
"All this word which I command you, that shall ye observe to do; thou shalt not add thereto, nor diminish from it."
This is the assurance that the Torah (i.e. the 5 Books of Moses), the Word of the living G-d, are forever unchanged; that, and the incredible safeguards taken by scribes to ensure that no mistakes are made. My brother is a scribe, and I am very familiar with the requirements. But don't take my word for it - the fact is that the portions of the Torah discovered at Qumran (the Dead Sea scrolls) are identical to modern Torahs. Further, every Torah is identical anywhere in the world, regardless of the denomination of the synogogue that owns it.