All,
Thanks for your help. After researching a little more and talking to the AINP hotline, here is what I found out. Hope it helps others.
A "certified copy" is a photocopy of the original document that has text similar to "this is a true copy of the original" written on it by a person who has the "authority to certify" a document. This text need
not be hand written, and it is very likely that the person will use a rubber stamp which has text like
this. After the person stamps on your photocopy, your photocopy is now called a "certified copy", "true copy" or "true certified copy".
So, who are the people who have the authority to certify a document? Like the other posters mentioned there are many people who do this, but a "Public Notary" in your area is probably the best person. A Public Notary is a person who can many legal abilities, one of which is the ability to certify documents. However, note that in some states in the U.S., it is
illegal to "certify documents" and so you cannot find anybody who does that! Check
here to see if it allowed in your state.
So, what should you do if it is illegal to certify documents in your state? Not sure. But, if you can get some notary to sign on the document and put a seal like
this, even though there is no text that says that this is a "true certified copy", it might be alright. At least, when I called the hotline and told the person that a notary has signed but the "true copy of the original" text is not there, she said that it was OK.