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.