I feel that there's a lot of value in how a finished PDF document is visually inflexible. This is how the document looks, and this will be how the document look

I feel that there's a lot of value in how a finished PDF document is visually inflexible. This is how the document looks, and this will be how the document look in the next generation PDF viewer on a completely different computing platform of a different type of device. If it works on my machine, it works on yours, too. (This is ignoring the dynamic PDFs with javascripts in them) It doesn't evolve with the electronic device, which means you might need to zoom and pan, but it also means that it probably won't be completely bungled. I've bought an EPUB which only works on iPad. If the screen is sized differently, or uses a different font, etc., the texts are all messed up. It simply wouldn't happen if the book was distributed via PDF.