How to assign limited access to a protected PDF file on a user basis
Using Locklizard Safeguard PDF DRM you can create a PDF that does not expire yet provide limited date access to it on a per user basis. So the PDF file expires on a different date for each user.
You can also make the PDF file expire on a date, so that regardless of user access expiry, the PDF will expire for all users on a fixed date. This may be useful for example if you want to prevent obsolete versions being in circulation after a certain time period has passed.
Safeguard provides total expiry flexibility as PDF documents can be set to expire or not expire, but user access to them can be limited to a date range.