After searching in documetation, in thawte and in openssl, I put here the solution in case anyone need it.
And you will probably, because all the entities will migrate to 2048 bit root soon (International recomendation).
First, you need all the root and intermeditate certificates, normally on .crt extension in BASE64 encoding.
Then you create a .pem file, copying all the certificates in one file
Apache has 3 directives to manage SSL in this case:
You must configure them in each Virtual host (If used).
This way all the clients will get a correct certificate and they will trust on the entities that issued the certificate.