Most printers allow you to change the quality of their output, with lower quality settings using less ink that higher quality. You can change this from inside PIRform. After clicking the Print button at the top left of Print Preview, you will see a dialog that lets you select a printer and set the number of copies, etc.
From there click the button marked "Preferences" and it will open up a dialog that allows you to change your printer's settings. You will see something like the screen below, but it will not be exactly the same as it is part of your printer, not PIRform. Each printer will have a section somewhere that allows you to adjust the quality of your output. Please refer to your printer's manual for further details.