Most of the requests that I get to notarize foreign language documents are for German documents, since German is the language that I know.
This morning I got a call from a Russian man, asking if I would notarize his signature for a Russian document.
Of course.
When I got there he showed me the document. I had him sign it, and then I notarized his signature.
What did the document say?
I have absolutely no idea.
A notary public does not concern themselves with the contents of the document. We notarize signatures, not documents. And Colorado notary law does not prohibit Colorado notaries from notarizing documents in a foreign language.
However, there are some measures that I took. The first thing I did was take a photo of the document with my digital camera. Whenever I notarize a document in a foreign language, usually for copy certifications, I keep a copy of the document for my records.

Also, I attached a loose certificate. So although the document is in Russian, the notary certificate is in English. And that is really all that is required.
I don't know the notary laws of all states, so the prudent thing for any notary to do is to make sure that their state notary laws allow them to notarize a document in a foreign language.