How to Sign a PDF Digitally and Know Which Signature Type Is Valid

Signing a PDF electronically eliminates the need to print, sign, and scan documents, and can be done in minutes using browser-based tools. There are three main signature types: a simple image signature, an electronic signature service that records an audit trail, and a cryptographic digital signature that invalidates the document if altered. Electronic signatures are legally recognized for many agreements in countries like the United States under the ESIGN Act and across the EU under eIDAS, though rules vary by document type. Certain documents, such as property deeds, court filings, or government forms, may still require stricter methods, witnesses, or notarization. Experts advise using a signing service with an audit trail for high-stakes contracts, and recommend tools that process files locally to avoid uploading sensitive documents.