Form W-4 pdf file saved on workstation security issue

We are implementing the W4 updateable PDF functionality and our security team has raised the concern that a file with sensitive information (SSN) is being saved on the workstation as part of the process.  We have many users who share workstations which makes the security concern even greater.   We have heard that masking the SSN is an option, has anyone tried other options to address the security risk introduced by storing the file on the workstation?