Adobe offers support only for Magento's premium version, which is aimed at corporate clients and is out of reach for most store owners. PrestaShop offers a paid support plan, which, unfortunately, is also on the steep side. You should be able to get the information you need without paying for official support, though. The two applications are still pretty popular, and there's no shortage of people who know them well and are willing to help. You can find plenty of helpful resources on the internet, as well, and if you're feeling stuck, you can always ask your hosting provider's support team for guidance.