Use the Folio Overlays panel to create and edit interactive objects. To open the Folio Overlays panel, choose Window > Extensions > Folio Overlays (InDesign CS5/CS5.5) or choose Window > Folio Overlays (InDesign CS6).
Why are interactive objects called overlays? When you create a folio, all non-interactive items on a page are compressed into a single image—PDF, JPG, or PNG, depending on the article’s image format setting. If you mask or cover interactive overlays that you place in the document, the overlays appear on top of the layout in the folio. Only another overlay can mask an overlay.