One of my ex-compatriots at QNX sent me this heart-warming tale…
This talks about a buffer overrun failure on the iPhone. Not too exciting.
However this statement from the article is golden as far as you are concerned.
When your iOS device tries to display the PDF file, that font causes something called stack overflow, a technical condition that allows the secret ninja code inside the font to gain complete control of your device.
Fonts have secret ninja codes!