We’ve received many questions recently about the differences between pdf format and epub format, so we thought it might be helpful to provide some details on the differences between the two formats.
PDF
PDF format was specifically designed not to be fluid, to the contrary; it’s meant to guarantee an identical display no matter what the support, without taking into account the size of the screen, etc. It’s the ideal format for preparing a document for printing on paper, since you can be sure that the layout you have prepared will display exactly the same for the printer as on your own computer. However, what makes it perfect for print is exactly what makes it unsuitable for ebooks, which must be readable in many different conditions, depending on the size of the screen and the needs and preferences of the reader.
To make pdf reading easier, on the Cybook Odyssey HD FrontLight, Bookeen proposes a reflow mode for pdfs, which simplifies the layout of your document to make it more readable on an ebook reader, which has a smaller screen than a PC or A4 format page.

Even with this option, we recommend that you avoid the pdf format whenever possible, unless your document has been specifically formatted for your Cybook and your personal preferences (texte size, choice of font…) since the inherent rigidity of this format will never allow a completely personnalised display.
EPUB
The EPUB format is specifically designed to provide an optimal reading experience on the support of your choice, by allowing the text to adapt to the size of the screen while still respecting the layout and formatting. EPUB allows you to modify the size of the text on the fly and to choose the font you prefer (did you know you can even add your favourite fonts to your Cybook? Just place the font files into the “Fonts” folder on your Cybook, then choose your favourite font from the menu while reading). Your Cybook even allows you to choose whether or not to activate justification, hyphenation, and even typographic ligatures if your font proposes them (for example Minion font, provided with your Cybook)!

Examples of typographic ligatures. Image from
wikipedia.
EPUB is the ideal format for ebooks. For an optimal reading experience, we strongly recommend you choose EPUB whenever possible.