I want to apply ITIN for my wife.

Per "http://www.irs.gov/Individuals/Revised-Application-Standards-for-ITINs" there are 13 documents that can be accepted for iTIN. As she lives in remote town, it would be easy for her to get certified birth certificate and certified voter id card (with photo and address) than to get her passport certified.

Can she courier the certified birth certificate and voter id card along with signed W7 form to me and then I apply for her ITIN here?

Will IRS accept such applications and documents (as she is in India)?

Yes, IF the voter ID card is a photo ID and IF the birth certificate is in English.

Also, the Form w-7 MUST be submitted with a tax return which, as a joint filer, SHE must sign as well as you.

Yes, IF the voter ID card is a photo ID and IF the birth certificate is in English.

Also, the Form w-7 MUST be submitted with a tax return which, as a joint filer, SHE must sign as well as you.

Thanks for your reply AtlantaTaxExert.

Her lastname (surname) changed after our marriage. Hence lastname in birth certificate and voter id card is different from Passport. Can this be an issue?

The name change can be accounted for on the W-7.

While all this is true, the BEST ID is STILL a passport.