I am looking for software that will allow me to sign a document and if the document is changed the signature is no longer valid. I also would like the signature for the document to be valid forever and not just for a subscription period.

Right now I can pay a notary public, get my signature notarized and that document is good forever. It does not even matter if the notary public kicks the bucket. Is it too much to ask to for some software that can perform a similar function?