Hereof is another stiff document word. It means “of this” — belonging to this paper, or about this paper. “On the date hereof” means on the date of this document. “The parties hereof” means the people this document is about. English built it as here + of, and it has been in the language a long time. Though actually, it is easy to mix up with its neighbours. Herein is in this document (the contents sitting inside it). Hereof is of this document (belonging to it, about it). Hereto is to this document (often “attached hereto,” meaning stuck onto it). The little words in, of, and to are doing different jobs; the here is the same “this official paper” each time. You will not hear hereof in a café. It lives in contracts, deeds, and formal letters.