By default, all files uploaded to Uploadfiles are given a unique ID or "slug" - this ensures nobody can stumble upon your files, and only those with the download link can access them.
To add even more security to your files, you can set a password on each file. To do so, login to your dashboard, hover over your file action button, then choose "Set password".
In the new modal, type in your desired password and click "save & close". Now, when you share your file, a password prompt will appear before it can be accessed.
To remove a password, simply repeat the steps above until the password modal appears, then click "remove current password"