It seems that no readers, including Adobe Reader as of now, support layers in PDF documents.
Support for layers would allow me to insert "popup" images that appear whenever the user clicks a certain phrase or area, or even just hovers with the mouse above it.
What mouse?
Hi tsuma,
Please try PDF Max, free on the AppStore (http://itunes.apple.com/us/app/id540572073) to see its threaded-comments feature is what you're looking for.
Cheers
"Corrected. I meant cursor."
What cursor? Are you using a device running the iOS operating system or are you using OSX?
Ah, sorry. I am talking about iOS only. No cursors, no hovering. However what I need is the feature when tapping an element brings up / hides a layer, in addition to having layer control via a "layers" menu or option (much like Adobe Reader on the desktop does).
To date all iOS PDF reading apps are built on an engine that does not have the ability to select which layers are shown and hidden.