What is a digital signature (and how it differs from an electronic one)

“Electronic signature” and “digital signature” are often used as synonyms, but they are not the same thing. An electronic signature is any electronic way to show you agree — from typing your name to placing an image of your handwritten signature on a PDF. A digital signature is a specific technology: cryptography and a certificate that prove who signed and that the file has not changed since. Here is what each one is and when you need which.

Electronic signature

An electronic signature is a broad category: a typed name at the end of an email, a checkbox “I agree”, a signature drawn with a finger in a delivery app, or a picture of your signature placed on a contract. What makes it a signature is the intent to sign and the agreement of the parties to deal electronically.

Many countries give electronic signatures legal weight for most everyday contracts. In the United States, the ESIGN Act (2000) and state UETA laws say a contract cannot be denied effect just because it was signed electronically. In the European Union, the eIDAS regulation recognizes simple electronic signatures too, while giving the strongest status to qualified ones. Some documents — wills, certain court and real-estate papers — may still need a wet-ink or a qualified signature depending on where you live.

Typical use: “please sign and send back” — a freelance contract, an NDA, a lease addendum, a permission slip, an invoice approval.

Digital signature

A digital signature is a cryptographic stamp. The signer has a private key, usually tied to a certificate issued by a trusted authority. Signing creates a mathematical fingerprint of the document; anyone can check it with the public key. If even one character in the file changes, the check fails.

That gives two things a signature image cannot: proof of who signed (via the certificate) and proof that the document has not been altered. That is why digital signatures are used for tax filings, government portals, tenders, and as the basis of “advanced” and “qualified” signatures under eIDAS. In a PDF, a digital signature shows up in the signature panel of a reader like Adobe Acrobat, with a status such as “signed and all signatures are valid”.

Side by side

• What it is: electronic — any sign of intent, often an image of your signature; digital — a cryptographic signature tied to a certificate.
• What it proves: electronic — that you agreed, backed by context (emails, audit trail); digital — who signed and that the file is unchanged.
• What you need: electronic — just your phone; digital — a certificate or an account with a provider that issues one.
• Where it is enough: electronic — most business and personal agreements; digital — wherever it is explicitly required.

Which one do you need?

• Asked to “sign and send back a PDF” or “send a signed scan” — an electronic signature is what they mean.
• Asked for a “digital signature”, a “qualified signature”, a certificate, or the document goes to a government body — you need a digital signature; an image will not do.
• Not sure — ask whoever sent the document. It is faster than redoing it.

How to sign a PDF on your phone

With your handwritten signature. On iPhone, open the PDF in Files, tap Markup, then “+” → Add Signature — step by step in how to sign a PDF on iPhone. For frequent or multi-page documents, Signature: sign documents lets you use a signature drawn with a finger or captured from paper with a transparent background, place it on one, all or selected pages, and save as PDF, JPG or PNG. No account; signing comes with PRO.

With a digital signature. Use a service or app that holds your certificate — the one your government, bank or e-signature provider offers. The signature is then embedded in the PDF and can be verified by anyone who opens it.

In short

• Electronic signature — any electronic sign of agreement, including your signature image on a PDF.
• Digital signature — cryptography plus a certificate: proves who signed and that nothing changed.
• For everyday “sign and send back”, an electronic signature is usually enough; where a digital or qualified signature is required, an image will not do.
• This is a general overview, not legal advice — rules differ by country and document type.