Note that document forgery is a "real crime" most everywhere - so if you were caught (perhaps due to some unrelated investigation) - it might not be the best idea.
I'm not saying you shouldn't break the law to preserver your anonymity (at your own discretion) -- I'm just saying it's something to take into consideration. If you for example fear that you might get dropped in a black site, fed polonium or pushed down some stairs over your on-line activities -- a little document forgery might be just the ticket.
