[marc]

The PDF has no 'notion' of the Layer from OmniGraffle, it's just a representation of the page.

To achieve the desired effect you'll instead have to set up another Canvas with the area you want to show/hide, and set the Actions to switch back and forth between this page, and the original.

Think of each Canvas as a static scene/image of each UI state you want to show; this can also be useful if you want to be able to print and mark up comments for individual states, and particularly multi-step processes.