I’d be surprised if the PA Secretary of State cared what language the document is in, but probably cares what language the notarial certificate is in. The apostille basically certifies that the notary had an active commission at the time the apostille was done, and that the notary’s signature looks just about the same as the signature on file.
One problem is whether the notarial act that the Russians want is one of the ones that a PA notary is allowed to perform.
Another problem is whether the Russians want the notarial certificate written in Russian or English. If they want English, you can just use one of the short certificates that PA issued after RULONA was passed.
But if the Russians want the notarial certificates in Russian, the PA SOS might not be willing to issue an apostille. Also, you would pretty much have to be a lawyer in both PA and Russia to figure out what Russian wording would convey the same meaning, in a legal context, as the English wording.