If you read digital comics, then you probably know that most show an entire page view at once. You might be zoomed in on one part of a page, but the entire page is loaded. With Marvel’s new comics, the artist is given the opportunity to use time as a story telling element. New page elements, larger frames, and word balloons appear as the reader clicks the next button.
The PDF duplicates the new features by having new material appear when you turn the page. There’s no DRM or code involved, so it should work with every PDF reader.
via Mark Waid