Can't delete sticky notes

Using Acrobat 9 Pro, my boss created a pdf with several sticky notes. I opened the file with Acrobat 8 Pro, deleted all the notes, and saved it with a new name. But when I open the new file, the stickies are still there. Is there some incompatibility beween Acro9 and Acro8 that's causing this?

(I have Acrobat 8.1.3, but the drop down below just goes to 8.1.2)