If you add a copyright symbol, it shows that you are serious about protecting your copyright. However, it's true that you don't need to. if you created the written work, the copyright is inherent. It is yours, and anyone who stole that work, or reused it as a major part or a whole without your express permission, would have a case to answer to you. Even if they attribute the material to you, they still need your permission to reproduce it. I hope that helps.