Set up dropbox or similar app for induction/training video -- 2

We have an induction/training video and we want to be able to securely send out a link via email to individuals or a porta that they can log into such as Dropbox etc. Want to get electronic signature that they have watched the video and understand its contents and then confirm for us that this has happened and have a record of that. Want the link to expire after a set date for the individuals that it has been sent to. We have the video already done.