Our WordPress document library plugin is designed to help you manage and display documents. It is not an e-commerce plugin and is not designed for selling documents.
If you want to sell documents then we have a tutorial on how to sell documents with our other plugins. There are two options depending on whether you want to use Easy Digital Downloads or WooCommerce to provide the e-commerce features that you need for selling online. Either way, you can then display your documents in a searchable table similar to the one in Document Library Pro.