Manage signatures for all people in the organization

Manage signatures for all people in the organization

Hello,
what is the best and easiest way to manage and update signatures for all employees?

We participate into fairs, so every 3 months or so we have to add a banner in the e-mail  for all addresses in our organization.

Adding it one by one is very time consuming so I was wondering: is there any way manage email signatures in a centralized way?

Hope question is clear.
Thank you
Antonio