Download formats: PDF vs ePUB
Some e-book platforms offer only one format, whereas others, e.g. ProQuest Ebook Central, often provide a choice between download in PDF or ePUB formats.
PDF retains the look and feel of the print book, the disadvantage being that the text displays the same way on all devices, regardless of screen size. On a smaller screen this results in a poorer viewing experience and you may have to scroll/drag to see the whole line of text.
With ePUB, the text flows automatically to support the size and shape of your viewing device. The ability to resize and reshape the text of the book ensures a much better viewing experience on mobile devices.
ePUB text can also contain links to other sections of the text or to external sources and functions better with screen reading software. ePUB texts may not feature page numbers, as the text flows differently on different devices.
Some e-book platforms offer guidance as to PDF vs ePUB, e.g. EBSCOhost.