PDF was developed in 1992 by Adobe to reproduce documents for prints just the way the sender sends it. Regardless of the computer or printer used, the goal is to have no alterations whatsoever to the original document. And the PDF format did this well. It works basically on most computers.
The PDB reader supports bookmarks, text re-flow, tables, embedded images, DRM and footnotes, it allows page mark with a bookmark or any part of the text with footnotes.
Apple iPad, iPhone and iPod, Blackberry, HTC/Andriod, Samsung, Palm OS but not WebOS, Sony Ericsson, Symbian, PocketPC the 2002 and earlier versions, Windows mobile phones