Want bookmarks to be displayed automatically by Acrobat readers

Using Acrobat Pro 8.0, I've created a collection of PDF documents and set up bookmarks. I've saved with the view bookmarks. But, when I open the file in Acrobat Reader 9.0, the bookmarks are not automatically displayed.

This must be a simple thing to do but I've not had any luck in finding out how to do this.

Hope someone can provide me with an answer.

Thanks!