The most consistent way to get a discount on a new license is through affiliate and partner promo codes frequently shared by users. These typically offer 20% to 30% off the retail price ($69.95).
Never download cracks or pirate software. Not only is it illegal, but it also poses a risk to your computer's security.
Set a price alert on Slickdeals or follow r/GuitarPro_deals (unofficial but active).