No law requires that you hire a lawyer to prepare or to be present when you make a will or codicil. The laws controlling how to make a valid codicil
Many states allow for your will or codicil to be unwitnessed, but usually specific circumstances or conditions must be present, and additional steps must be taken to prove that the document was written and signed by you. In addition, if you do have individuals witness your will or codicil, your state may require that they sign a statement containing very particular statements or language.
There are many ways you can prepare and execute a proper codicil or will without the help of an attorney. There are many reliable resources for preparing simple legal documents on your own. One resource is Nolo, a self-help legal publishing company.
A few words of warning: You'll want to be sure that the wording you add does not conflict with or invalidate the rest of the will. If you have questions about this it may be worthwhile to hire a lawyer for the limited purpose of verifying that.
vary from state-to-state. In most states, however, you must sign and date it. And at least two people, neither of whom are entitled to take property under the will must witness your signature and sign your will themselves.