[SebastianKra]

It is needed. I hate reading pdfs on my 24" or 32" monitor. I hate reading them on my Phone. The main thing that my father complained about when switching from Blackberry to iPhone, was missing PDF reflow feature. Basically the only screen where I find pdfs comfortable to read, is on the 12.9" iPad, and only if the author has the same font-size preferences as me.

[Shorel]

That is the main flaw of the PDF file format. It is by design.

If we want documents that work well on all screens, then we use EPUB.