title: Annotate PDF within iPhone SDK
body: <p>I have managed to implement a very basic PDF viewer within my application, but was wondering if it was possible to add annotations to the PDF. I have looked through the SDK docs, but not found anything. I have 2 questions really:</p>
  
  <ol>
  <li>Is it possible to do this?</li>
  <li>What is the best approach to take?</li>
  <li>Is there a framework or library that I can include to assist with this?</li>
  </ol>
  
  <p>Thanks.</p>