Security Restrictions might require Deliveries to be protected with a password. E-mail and File subscriptions can be password protected when the delivery format is set to PDF, Excel, Plain Text or CSV. Therefore the content must be compressed, then a password for the zip file can be specified in the advanced options when creating a new subscription in Distribution Services.
To do so please tick the compress content checkbox and specify a a password in the Advanced Options as seen on the screenshot below:
