In my last post, I took KFNB Reading Technology to task for developing its own proprietary format for eBooks, and stated that PDFs can provide the same "page fidelity" experience as KFNB's Blio eBook reader. There's a good reason to create a new format, however, and it lies at the heart of PDF itself.
There are lots of ways to create a PDF file that looks good when viewed in a PDF reader, but the internal structure of a PDF file can vary widely, depending on the tool used to create it and even the order in which it was created. For publishers, Adobe's InDesign and Quark's QuarkXPress are the two most popular tools for laying out books. These tools can then generate PDF and ePUB files, and it's those files that are used to create eBooks. However, there are many other tools that can create PDFs, and Adobe's own print drivers can create PDFs from almost any document. Some publishers have written their own page layout and conversion software, and there are dozens of format conversion services around the world that can accept files in a variety of formats and output PDFs.
The internal structure of a PDF is very important if you want to create notes or highlights, select text or perform text-to-speech. Adobe has what's generally considered to be the best PDF rendering technology in the industry, and they handle the variety of ways that a PDF can be constructed very well. However, if you need to write your own converter or renderer, you have to handle all the myriad PDF variations.
That's one reason why a company like KFNB would decide to create its own format and require publishers to convert their titles into its format rather than PDFs. By enforcing a more consistent internal structure, KFNB could bypass many of the problems faced by PDF renderers. However, it still results in compatibility issues--eBooks in KFNB's format can only be read with KFNB's readers. If KFNB goes out of business, no new readers will be available, and if there's DRM on the KFNB eBooks, it may be impossible to use them in the future.
That's why I would have preferred to see KFNB "bite the bullet" and do the hard work of parsing PDF files in its reader, instead of creating its own format and insisting that publishers use that rather than PDF.