This addon is definitely TOP module to create popup windows in PrestaShop. Module contains many features to display popup there where you want (selected pages, whole website, etc.). This PrestaShop module allows to create responsive popup boxes with different contents for each type of device (PC, tablet, mobile). You can read more about this prestashop addon on official module website
You can find there only valuable solutions for your e-commerce shop based on PrestaShop engine. Search the best plugin for your store that will meet your requirements and just use it.