The meaning of 참
I’ve seen 참 used and I have no idea what it means. A Korean man said “You’re so beautiful” in English and it was translated as “당신은 참 아름답군요.” So, does 참 mean “really” or “so?”

Question

Answer

As you know, it is hard to translate a Korean word into English sometimes.

참 is a noun. it means "truth". 
참으로 is an adverb. it means "with truth, really, truly"
참 is also used as a contraction from of "참으로"

너는 참 아름답다 literally means "you are beautiful with true words"/"My words are true, you are beautiful"
You don't need to mind the English meaning of "really" or "so".
참 means maybe somewhat between "really" and "so" in English.

Answer

Yes. It is the meaning of emphasis.
followings are all same.

당신은 참 아름답군요.
당신은 진짜 아름답군요.
당신은 정말 아름답군요.