If you still want the print dialog box to pop up in order to be able to change the printer, you could also just alter the script on the standard print button. For example:
xfa.host.print(1, "0", "0", 0, 0, 0, 0, 0);
Parameter 1 allows the print dialog box to come up, parameter 2 ("0") is the starting page and parameter 3 (also "0") is the ending page. So this script will print page 1 only of a multi-page document and still allow the user to change the printer.
For a full explanation of all 8 parameters search for "print scripting method" in the LiveCycle Designer Help.