installing multiple printers

I am running a windows 98 OS and need to install 5 printers (3 serial and 2 parallel). I might even need to add a fourth serial in the future. I am having problems installing both a multiple serial card and a multiple parallel card. This computeris used for shipping and every company needs to have there own printer. I am looking for any solution to be able to run all 5 printers at the same time. Is there a max amount of serial and parallel ports available?