If you have a version that is not too old, yes.
 
The first choice in SO-S is "Print Posted Packing Slips?". Click the check box and "SO Number" changes to "Invoice Number".  
 
Note that the above only works if the Invoice has been Posted.
 
If you want to print a PS after the SO has been Invoiced but not Posted, you would normally have to re-print the Invoice and mark it not Printed, print the PS and then re-print the Invoice again.
 
However, you don't have to do all that just by checking the "Print Non-Released Line" box. It would seem that when you mark an Invoice Printed the lines no longer show as being Released, even though they really are.

Lynn, you are  correct. I am currently stuck at DBA 2002.1 SP2.
 
I really need to try and update this program.  HELP.