The sample you found is probably as good as it's going to get. Rights Management policies can either allow or prevent printing, there is no "permission" to set the number of copies that can be printed.
The policy is checked when the document is opened, if the policy is dynamically changed (i.e. the permission to print is removed) it will not take affect until the document is closed and re-opened, so in theory, the document can be printed multiple times when opened the first time.
Also, there is no way to prevent someone from printing once and photocopying it many times.
Thanks a lot for your answer. It is actually very usefull.
As a result, I am now looking for an alternative solution with the Adobe LiveCycle Designer, in order to add a custom print button on the form (instead of the real one), but i have no clue yet if i will be able to interrogate programatically the Right Management module of LiveCycle, to confirm the permission.
From what i have seen so far, it looks very uncertain...
If you have other tips, i'll be very interrested.