Question: How can I create a PDF form to be completed and saved with comments using only Adobe Reader?
Answer: If you created the PDF in Acrobat 9, you can select Advanced > Extend features in Adobe Reader and click save. Make sure your files is completely finished and save it under a different name. Using this feature will cause other form features to be disabled.
If you are using Acrobat X, you will select File > Save as > Reader Extended PDF > Enable additional features.
You’ll find this and many other useful short video clips at http://tv.adobe.com/watch/acrobat-tips-and-tricks/enabling-usage-rights-for-adobe-reader/