How to create virtual products in PrestaShop 1.5-1.6
If you want to sell virtual products, in the admin panel of PrestaShop there are options with which you can create such products. Most of the settings for virtual products are exactly the same as those for standard products so in this article we'll only go over the options that are specific to virtual products.
To add a product go to Catalog menu>Products sub-menu in the admin panel and click on the Add new product button. On the page with the general product settings that opens mark the radio button Virtual product. It's at the top of the Information page. When you do this the Shipping tab on the left will automatically disappear and a tab labeled Virtual Product will appear. If the virtual product is also a downloadable one (e.g. music, video, text file, etc.), click on that tab. On the page that opens select Yes for the option Does this product have an associated file. When you do this a few more options will appear.
From the File option (labeled Upload a file in PrestaShop 1.5) you can select the file that customers will be able to purchase and download. Click on the Add file button (in PrestaShop 1.5 it's Browse) and select the file from your local computer. After you do this the name of the file will appear automatically in the field for Filename. If you want to limit the number of times that the purchased product can be downloaded, put the number in the field for Number of allowed downloads. In case you want to set an expiration date after which the product can't be downloaded put the date in the field for Expiration date. If you want to limit the number of days that the virtual product can be downloaded after it's purchased, put that number in the field for Number of days.
After you're ready with the options click on the Save and stay or on the Save button.
Customers can order virtual products on the frontend in the same way as other products. After they order the product(s) and the status of the order is changed to Payment accepted, the virtual product can be downloaded. They'll receive and email with a link with which they can download the product, or they can do it from their account settings from the frontend of your store.
For screenshots and some more details you can check out the tutorial on how to add virtual products in PrestaShop.