It depends on if you are using a text (PCL) queue, or a PostScript queue and if you are using a local or remote printer.
The qprt command is the 'virtual printer' command and for a printer that has the capability, you can switch a text based printer with 'qprt -z+ -Pqueue filename'. or -z1
You don't have to create separate queues. I you use the lp or the enq commands, then you can use the -o -z+ flag
lp -o-z+ -d<queue> file
Then of course at AIX 5 you could be doing System V printing. With PostScript files, usually the orientation is set inside the file and you can't change it from a queue.