You can specify a username with lpr as per this question.
Ubuntu uses CUPS for printing so the easiest way is to use the web interface. You find it at: http://localhost:631
. Change the URI for the printer to lpd://firstname.lastname@SomeHostname/SomePrinter
or change the conf file in /etc/cups/printers.conf
This will make it permanent.
A new user is not necessary.