Keep in mind that they are going to cost you much.
If you have two ssl certs for a domain.com and then a sub.domain.com, these two certs cannot be installed in IIS servers upto version 7.5. IIS8 on Windows 2012 supports it though.
Note: you need to create the csr on the machine where you will be installing the ssl certificate. otherwise, the private key is not present and the ssl certificate is not installed properly.
Got this below information from elsewhere...
JBrunelle April 9, 2014 at 8:01 am If anyone is still watching this thread… I came across this with a digicert cert as well. What I did was import it anyway into IIS. After adding it, but before it disappeared I right-clicked and selected view on the cert, went to the Details tab, and selected copy to file. Selected to export the private key, and assigned a password. Then I refreshed (cert was gone) and re-imported the now .pfx cert and entered the password.
Worked like a ch…