Your journal is a public record, which means periodically someone might ask to examine it. But it is generally not the type of public record available for anyone to peruse for any reason. In fact, it's your job to keep the contents from prying eyes because the information you record often is sensitive and could easily be used for nefarious purposes. Legitimate requests, however, should be honored.
The best way to separate legitimate requests from "fishing" expeditions is to require a formal written request. Typically, the request should include the name of the signer, the approximate date of the notarization and the type of document notarized. You also should ask the requestor to present valid ID.
Once these conditions are satisfied, make sure to cover up other entries on a journal page when making a photocopy. This protects the information about notarizations unrelated to the request.