When you go to the 'Print Center' you should see a list of forms that will be printed by default. However you should see a square check box at the beginning of each set of forms. By deselecting the forms one at a time you should be able to then print only the remaining set of forms. As a simple alternative you could simply print the forms twice; then manually you could select only the set to be mailed in each separate envelope
If you were to send both sets of forms in the same envelope you risk the tax department receiving the forms will get things confused.
