You need to set up 2 print queues, one defined for portrait, one for landscape. You can set one as the default lp.
Depending on which way you want to print you will then call that queue.
Typically I have called our printqueues "port" and "land", with "port" being the default PQ.
So to print I would do this:
lp -dport or lp = portrait mode
lp -dland = landscape mode
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