PDF format allows you to view an e-book in the same layout as a print copy of that book. This enables you to see the book in its original design, with diagrams, photos, illustrations, and text appearing exactly the same as in the print book. However, you will be unable to make any adjustments to the font or presentation. ePUB format strays from the layout of the print book and allows the text to reflow based on the text size and font you choose. This enables a device to reflow text in a way that more appropriately fits the screen size. If you¹re planning to read your e-book on a device with a small screen, ePUB is generally the preferred format.