Is it possible to detect when a user is printing something from their browser?
To complicate matters, if we are presenting a user with a PDF document in a new window is it possible to detect the printing of that document ( assuming the user prints it from the browser window)?
The closest I've been able to find is if we implement custom print functionality (something like this) and track when that is invoked
I'm primarily interested in a solution that works for internet explorer (6 or later)
Simple answer: No.
For IE maybe it is possible to write custom ActiveX application that can monitor everything you want, but this will not work for pdf's or other non-html content.
In Arcobat, the WillPrint event will fire before the printing starts. If you're doing it from Adobe Acrobat, from the menus chose Advanced ... Document Processing ... Set Document Actions ... Select "Document will Print" option ... edit and then you can write the javascript function you desire. The printing will continue, but this would be the place you'd insert watermarks. If you are looking to prevent printing, you need to set the document security appropriately. If you are looking to stop printing an incompletely filled out form, you need to use XFA (drawbacks of this approach are that viewers are required to have Acrobat 9+ and you'll need LiveCycle to create the forms.)