Custom certificate (plugin)

Hello, Here is my problem: I have custom user profile fields with names of companies (they are all checkboxes), and I want them to be listed in the certificate. Here is an example: I checked Company1, Company2, Company4 in my profile. The certificate should look like this: Companies: Company1, Company2, Company4 (sorry, if it seems too obvious) Can anyone help me? Thanks, best regards, Vitéz