To mitigate the risk of confidential documents being left unattended in Multi-Function Printers (MFPs), implementing an authentication factor that requires in-person action before printing (such as PIN codes or badge scanning) is the most effective measure. This ensures that documents are only printed when the authorized user is present to collect them, reducing the risk of sensitive information being exposed.
References = CompTIA Security+ SY0-701 study materials, particularly in the domain of physical security and access control.