Better not load any PDFs on your iPhone for a while, not unless you want to risk handing over total control of your device to hackers. The exploit affects all
iOS 4 iOS 3.1.2 and higher devices, including the iPod touch and the iPad.
The malicious code lurks inside a font inside the PDF and when you go to view the document, it causes something called a “stack overflow” which fills up the memory. During the ensuing crash, the program can slip into your device and do anything it wants. Anything, from deleting files, to install secret monitoring programs, to automatically calling 911 every time you make a phone call, to constantly shouting insults at you. Anything that can be programmed can be done.
So until they patch this bug, best just wait to view any PDFs until you’re at your home computer.
Apple Security Breach Gives Complete Access to Your iPhone [Gizmodo] (Thanks to GitEmSteveDave!)