When you need to convey a message or indicate an action, there are many synonyms for the phrase "sign for" that you can use. Some commonly used synonyms include "agree to," "acknowledge," "give the green light," "authorize," "endorse," "validate," "sanction," "approve," and "certify." These phrases all indicate that someone is giving their consent or permission for something to happen. Depending on the context, some of these synonyms may be more appropriate than others. For example, "validate" might be a better fit when referring to a document, while "endorse" could be used when talking about a particular product or service. Whatever synonym you choose, make sure it accurately conveys the intended meaning.