Remove Comments from a PDF
First things first, if you use the "Examine Document" feature and remove the comments, the changes will be permanent when you save the file! So for the example above, do a quick "save as" before you run examine document. To get started you will need the document containing the comments open in Acrobat. Once the document is opened you simple choose Document-Examine Document from the top menu. This will pop open a window that looks like this.

As you can see the "Examine Document" feature removes much more than just the comments. If certain items are contained within the pdf they will be displayed and you can simply check which ones you want permanently removed. Once you have made your selections just simply choose "remove all check items". Remember that the changes will be permanent once you SAVE the file. So if you make a mistake just close the document without saving and then reopen. Once you run "examine document" you will be prompted with the following screen that shows it was successful.
It is a great new feature for Acrobat and can really make things simple when communicating information to others. I could see this widely used in Document Control groups that are responsible for published deliverables. It is also insurance that everything has been removed, versus risking that it was done manually.
Have fun,
Jonathan