Nowadays Apple gives it away for free, but it used to be part of the paid iWork package (or bought separately from the Mac App Store). I believe there was also

Nowadays Apple gives it away for free, but it used to be part of the paid iWork package (or bought separately from the Mac App Store). I believe there was also a time period where it was given to users who activated a new Apple product, but for people still running older machines had to pay.