I doubt that you were able to do this in the past with just Acrobat. You must have used some other tools that got installed in Acrobat.
Take a look at a blog post I did a few years ago about this subject: http://khkonsulting.com/2009/03/splitting-pdf-pages/
Make sure you read the comments as well, there is some information in the comments about installing it in Acrobat versions newer than 9.
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com