Your mobile device must have wireless connectivty to a printer.
To print a secure message:
Note: If the print icon is greyed out, the the mobile policy of your organization prevents you from printing secure email or attachments.
Note: If the print dialog screen remains open for five minutes, the Voltage SecureMail app closes for security reasons and displays a system notification in the notification drawer.
Message printing is only supported on Android 4.4 and higher.