Since this is a DOSBox problem, it should go in the DOSBox forum. However, DOSBox is only intended for use with games, not applications, so do not expect to get much assistance.

If the parallel printer prints fine, why don't you just use that?

Also, are you using the Megabuild version of DOSBox?

some recent mainboard doesn't have any LPT ports.

most old-dos program simply can't print when running on that machine via NTVDM, as such apps usualy try to talk directly to LPT ports.

for such computer, some could try DOSPRN (shareware): http://www.dosprn.com/dos-print.htm