Rental Contracts are available in version 1.4+
Most of the rental contract can be edited by using rentals > settings > rental contract and then editing your terms, header, footer, and title. But if you want finer tuned control you can edit the actual html template.
pdf.phtml template editing #
The template is at app/design/frontend/base/default/template/payperrentals/contractpdf/pdf.phtml you will want to copy this to the design package and theme you are using. For example if using rwd default theme you would copy it to /app/design/frontend/rwd/default/template/payperrentals/contractpdf/pdf.phtml