I just finished a call with Principal because I was unable to locate any information about PMDIX on its site. He searched as well and looked for other resources at Principal. Nada. Also, I searched the site for PMDAX but received a 404 error. So unless we both really missed something, there isn't any information of the site about this fund.
I own PCBIX, which does have detailed information about it at Principal.
I have followed PMDIX for a while but don't own it, and like you, have others in this "sleeve." PMDIX would fit in with what I own (and I've run all the numbers), but I already think I have enough diversification.