How to migrate CA from 2003 to 2012

Official procedure:
https://technet.microsoft.com/en-us/library/ee126140(v=ws.10).aspx

Step-by-step:
http://blogs.technet.com/b/canitpro/archive/2014/11/12/step-by-step-migrating-the-active-directory-certificate-service-from-windows-server-2003-to-2012-r2.aspx

Some scripts:
http://blogs.technet.com/b/pki/archive/2010/04/20/disaster-recovery-procedures-for-the-active-directory-certificate-services-adcs.aspx

Another blog:

http://blogs.technet.com/b/xdot509/