Comments were added to a PDF created in Adobe Acrobat X on a Windows 7 PC. These comments were then viewed in Adobe Acrobat X on a El Capitan MAC. When the comments were added they are 9 point. When you view the comments on the PC they appear as 9 point. When you view the comments on the MAC they appear as 80 point. Does anyone know why this happens and how to fix it?
Acrobat X is not supported on Mac OS X El Capitan, so it's not surprising that you are seeing weird things. Unless this also happens in a version that is supported under El Capitan there is unfortunately nothing you can do besides either upgrading Acrobat, or downgrading Mac OS X.