Now, although the file prints out two different pages, each of those pages actually goes through but the backside is not marked. It is as though there are two different mechanisms sending a formfeed to the printer and the second one creates the blank backside. I will dust off my Postscript bible and see if there is anything in there.
I think you need a different command line interface. I believe you mentioned Linux, so try here and see if there is anything useful. If you do a search from hp.com for something like 'unix command line user lp interface' and see where it leads you.
http://hplipopensource.com/hplip-web/index.html
