Adobe Acrobat X allows you to comment on the documents while in comparison there are hardly more than two commenting tools in Adobe Reader. The Reader Comments encompass notes to mark changes and highlight text along with other various tools that he can use. If you want to send this file to someone who does not have Adobe Acrobat but only has Adobe Reader and you want him to completely utilize the PDF Reader Comments, then you can save your file in a particular format to provide him with enhancement in the tools of Reader. Follow this step by step tutorial to learn more about enabling full commenting in Adobe Reader.