Regarding Pega Certifications, the Certificates are already mapped to my personal primary PDN Account " xxxxxxxx@gmail.com ". 

I'm unable to add secondary mail address i.e., "xxxxxxxxxxx@companyname.com" getting an error message like already have a Pega PDN account. Since this ID "xxxxxxxxxxx@companyname.com" also is the primary PDN Account.

Kindly, please suggest how to map the certification to the  Primary PDN Account ( "xxxxxxxxx@companyname.com") from personal primary PDN Account (" xxxxxxxx@gmail.com ").

So, that certificates will map to both email addresses.