If your documents are notarized and apostille and if the OKPAY's company jurisdiction is part of the  Hague Convention, then OKPAY MUST accept your documents.

If OKPAY jurisdiction is not part of  Hague Convention then your docs must be legalized by the diplomatic/consular mission of OKpay's jurisdiction(i don't know who it is) in your country.

So, find out where OKPAY is registered