It depends on what you are trying to say.
"proud" can be translated to many different ways depending on the situation.
1. 어엿한: expressing self-awareness
2. 당당한: similar to above, but much much stronger, thus rarely used
3. 자랑스러운: it's used ONLY when you are proud of someone or significant achievements. It's also an extreme expression that's rarely used.
I am proud mother of three children:
저는 어엿한 세 아이의 엄마입니다.
"자랑스러운" would be a total nonsense in this case. Beware of bogus translations here non better than peeking at bad dictionaries.