Donate & Download is a plugin that allows to distribute files through donations. People can decide how much to donate and what payment gateway to use for that (PayPal, Payza/Alertpay, Skrill/Moneybookers, Authorize.Net, InterKassa, EgoPay, Liberty Reserve, Bitcoins (via Paysius)), but you always can set minimum limit of their donations or even set fixed amount for each file separately. Once donation completed, the plugin automatically sends temporary encrypted download link to donor's e-mail address.