Adobe Digital Editions support

[HarryT]

Originally Posted by Abelturd

Actually, PDFs make excellent ebooks if you format them right. Of course you can't expect a PDF formatted for the size of A4 to display neatly on a device with 6" screen.

Given the fact, however, that the ability to change the size of the font is one of the main advantages of eBooks compared to paper books (I always increase the font size if reading in poor light, for example) then why select the one and only document format which effectively removes that choice?

[Abelturd]

You can always make 2 or 3 versions with different font sizes and switch between them. Though then it might be a bit tricky to find the spot in the book where you left off (you could look up a sequence of words on the last page in adobe reader and remember the page nb. and go to that page nb. on cybook; clumsy I know).
But besides changing the font size, something I do very rarely, you usually don't do any on-the-fly changes to the ebook on cybook, so pdf, although not perfect, is for me personally still a good alternative.

--Edit
It's possible to figure out a conversion coefficient between two font sizes.
E.g. between font size 10 and 11 it's in my case about 1,08 .
So if you left off at page 50 in the ver. with font size 10, then in the version with font size 11 you have to go to page 50*1,08=54.
I know it sounds silly, but it works.