Documents Seller is a precious component for operating digital download systems. We developed a new personal publishing library and adopted this component. It was easily installed and we could understand how to configure it promptly. In addition, the developer of this component was willing to support us by modifying some part of the code in order for us to localize it to our country. Thank you for your help, Tuan. In Japan, the payment gateways included in this component are not available except for PayPal. However, offline payment function will work well instead. I recommend you to try this for realizing digital download sales easily.