Here is a great survey on PDF preflight, that which many also call postflight, which was introduced in this blog post:

Posted by Marco on Jun 23, 2009 in cPDF
In 2008 Enfocus wanted to find out who exactly their clients were. They held a survey. 4.840 users responded. Now who was using what kind of software and on what platform? Where do they live? What’s their primary business? How frequently do they use PDF-files? Do they even check incoming PDF files? And… what were the errors those files contained? See: http://www.digital-engineer.net/archive/entry/preflighters-around-the-world-this-is-you/

The most common preflight problems with PDF print-jobs.