First, the Apostille is not recognized all over the world but only in states party to the Hague Apostille Convention. It is not a notarization, it is a kind of legalization. How I did it: Went to see an escribano, got the poder, went to the colegio de escribanos to get the Apostille. I do not know whether the document has to be in Spanish or not but the Apostille will most probably have to be translated to English. Here's a useful link
http://www.argentina.gov.ar/argentin...8&tramite=1501