How is it different to a normal PDF document?
A normal PDF is a static document; the Digital Publication is an interactive magazine/catalogue/book. Fully customisable to your specifications, you can include many different features. Give your readers the full picture by embedding videos to show much more that the standard snapshots. Embed presentations, hot-link any text or image, to make it easy for your readers to access more information or contact you about what they have just read. Or why not include interactive quizzes or a customer feedback form so your readers can tell you what they think? All this and more is very easily done with out Digital Publishing System.