I've been bitten by this "security feature" recently and digged up an ancient Adobe account to respond to the ludicrous statement:
"Because silent printing is a security risk – and unlike our competitors we CARE about security!"
Dear lrosenth,
The security issue you refer to is described here: http://www.fortiguard.com/advisory/FGA-2008-04/
It affects your javascript API and is a legitimate security flaw, but has nothing to do with MaxPr's question.
Any application, once executed, can print to any printer the machine has access to without user interaction. Adobe reader has no special magic privilige to do so, hence you are not improving security, you are just restricting automation of your software.
This new behaviour has also broken the file association verb "Print", in that it now causes Adobe to open, show the document momentarily, close the document, but leave Adobe Reader running. No amount of hand waving will persuade me that this is correct behaviour. It is ugly and incorrect and you should be ashamed. Adobe Reader version 4.0 from 1999 could do this correctly.