Dignitatis Humanae 10 tells it true: no one is to be forced to become a Christian.
This doctrine is contained in the word of God and it was constantly proclaimed by the Fathers of the Church. The act of faith is of its very nature a free act.
“(T)he reasonable and free submission of faith” is an absolute requirement.
In consequence, the principle of religious freedom makes no small contribution to the creation of an environment in which men can without hindrance be invited to the Christian faith, embrace it of their own free will, and profess it effectively in their whole manner of life.
So there we have it.