well, an obvious option is to simply pause the print queues and watch them yourself. I'm assuming you would rather just shoot yourself in the head.

I currently have two different print monitoring programs under evaluation. One is ranger print manager, but I very much doubt this will suit your needs. The other is the geneva logic print manager.

Both of these are pitched at schools, but they might solve your problem. I know ranger print manager can't restrict by doc type, but you can charge by page.

One option would maybe be to get any print charging software and setup that and your applications like this:

1) anything that can print set to A4 paper size
2) anything that can't print set to letter paper size
3) prevent users changing paper size
4) charge 10p for an A4 page, £10,000 for a letter page
5) set credit limit to £10

so if they try and print from a denied app, it comes as letter. The print manager says "not enough credit" and drops the job. They try and print from a valid app, they can print up to 100 pages. Obviously the precise numbers are up to you, but you get the idea.