Two Roads Diverged
Microsoft: "PDF is a great solution where you need to ensure that a document will faithfully reproduce when printed to a fixed page size. In the future, though, one of the key consumer benefits of e-books will be the ability for content to dynamically reflow across multiple devices -- allowing consumers to move their e-books from a laptop to the Pocket PC and back again, as just one example, or from a purpose-built reading device to a PC.
"This was one of the factors that collectively drove the formation of the Open eBook Authoring Group and the Open eBook Publication Specification, which has been adopted by a broad cross-section of the e-book community, including Microsoft, Nuvomedia and Softbook. Microsoft Reader was designed to facilitate that kind of reflow across the broadest possible range of devices. We believe that flexibility, coupled with Microsoft's digital rights management solutions, will be a compelling customer proposition."
Author's Commentary: According to respected digital designer Charles King of Unlimited Publishing, PDF works best with a fixed aspect ratio, rather than a fixed page size.
However, the fundamental choice remains: faithful reproduction of page design, versus the ability to more easily reflow across screens of different shapes. This echoes the dilemma faced by Web designers. Content creators and designers instinctively tend to favor systems that afford them greater control of presentation to readers; yet the marketing advantages of more flexible presentation (read: more potential customers) are equally compelling for publishers.
How is copyright protection achieved?
Adobe: "PDF Merchant encrypts PDF files and allows the encrypter and seller to control permissions for printing, copying and annotating documents to fit their business models. When content is sold to a customer, the seller has several easy-to-set options for locking content to a user's CPU ID, user ID, local hard disk or portable media.