Sharing a digital signature with others - how to?

I have an executive who has Reader DC installed and has a digital signature set up.  He wants to share this signature with his admin assistant so that she can sign documents for him as she manages a lot of items that come in through his mailbox.  How can he share his signature with her easily?  Not one we want him to have to spend a lot of time on.  On previous versions he simply copied a file and sent it to her but latest version doesn't seem to work that way and it looks like the signature is stored on a server rather than locally.  What's the solution?