As we are talking about a Kobo device, you might be able do this without editing the book. The KoboTouch driver supports adding some CSS to all stylesheets in the book during the send to the device. The instructions are in
here. Using @page with this might not work as they are treated a little differently than other styles. Part of the reason for doing this was to have a way to remove @page styles, but I have forgotten whether they will be put in if they don't already exist.