Hi Tatopitta,
Good question! You can buy a code-signing certificate from a third party - like Verisign - and use that anywhere connected to the Internet (and anywhere that trusts Verisign! :)). The downside is that they are expensive. I think ~$500 for a code-signing certificate.
If you are using CA that is installed on your server, however, it will likely require domain trust. If you're target user is not part of a domain that trusts the domain where your CA is running, it won't work. It may also be tough to set up the domains to trust one another.
Good luck!
Patrick Halstead
Project Manager at Qdabra