Creating a percentage discount code, meaning the customer enters a specific character string at the end of order process, and gets X% discount on his order, is pretty easy – and it is even a standard functionality of Prestashop, called a Cart Rule in latest 1.6 version.
To create a discount code, in the administration panel, go to Price Rules => Cart Rules
Cart Rules entry in Price Rules menu
There, click Add new cart rule
Add new cart rule option in Cart Rules menu
In the INFORMATIONtab, enter the discount details : name, description, and the code you want to use, or use the Generatebutton to have a code randomly generated by Prestashop
Cart rule information entry
In the CONDITIONStab, enter your specific conditions (if any) : customer selection, date range, order amount, number of coupons, …
In the ACTIONStab, select how your discount will work. For example, to apply 15% to all orders using the coupon, select the Apply a discount => Percent (%), and enter 15 in the Valuefield
Selection of percentage discount type and voucher value entry
Save your Cart rule, and see it successfully created in the list of cart rules.
Cart rule creation success confirmation
You can then see it working by creating an order, and entering the coupon code in the VOUCHERSfield. The cart values will be automatically recalculated.