How to sign a document with OTP verification

Emailing a signing link proves the link reached an inbox. It does not prove who opened it, and for a document that matters, that gap is the whole question. A one-time code closes most of it: the signer gets a code, enters it, and cannot sign until they do, so the record shows a second channel was used and not just an email that could have been forwarded.

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What you can do

How to sign a document with OTP verification

  1. Prepare the document and mark where each person signs.
  2. Turn on verification for the signers who need it. SMS verification signing sends a code to their phone; email verification signing sends it to their inbox as a second step.
  3. Set an access code to open the document if the contents are sensitive, which is separate from the signing code and can be given to the signer by phone.
  4. They enter the code, sign, and the audit certificate records which checks were passed and when.

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Frequently asked questions

How does OTP signing work?

The signer opens the link, and before they can sign, a one-time code is sent to their phone or email. They enter it, and the code and the time it was used go into the audit record. It is the same mechanism a bank uses to confirm a payment, applied to a signature.

Does SMS verification prove who signed?

It proves whoever signed had the phone, which is a long way further than an email link on its own and short of proof of identity. Nothing electronic proves who was holding a device. This is why the audit certificate records what was actually checked rather than asserting who the person was, and why a full ID and selfie check exists for documents where the difference matters.

What is the difference between an access code and a one-time code?

An access code is a static password you give the signer yourself, usually over the phone, and it gates opening the document at all. A one-time code is generated per signing and sent by us to their phone or email. They solve different problems and are often used together on sensitive documents.

Can I require ID verification instead?

Yes, where the document justifies it: a government ID scan with a selfie and liveness detection, checked before signing is allowed. It takes the signer a couple of minutes rather than seconds, so it is worth reserving for documents where an impersonated signature would actually cost somebody something.

Is it free to sign a PDF online?

Yes. You can fill in and sign a PDF for free with no account, you only pay when you download a finished document ($1.50 per document pay-as-you-go, or unlimited on any paid plan). sign a document with OTP works the same way.

Is signing a PDF online secure?

Yes. Files are uploaded over 256-bit TLS, processed in your browser session, and automatically deleted after one hour. Each signature is bound to the document with a SHA-256 tamper-evident seal, so any later edit is detectable.

Are electronic signatures legally binding?

Yes, electronic signatures are legally binding for ordinary business documents in 190+ countries under the US ESIGN Act and UETA, the EU eIDAS Regulation, and equivalent laws worldwide. Courts look for intent, identity and integrity, all of which PDF Verified records.

Do I need to install anything?

No. Everything runs in your browser on desktop or mobile, no app, plugin or download required.

What PDF Verified is, and what it is not

Electronic signature law is settled in broad terms and specific in the details. The ESIGN Act, UETA, eIDAS and their equivalents recognise electronic signatures across more than 190 countries, and what decides a particular case is intent to sign plus evidence connecting the signature to the signer, which is what the audit certificate records. Certain document types carry their own formalities wherever you are: deeds, wills, some property instruments, and anything requiring a witness or a notary. Sign only what you are authorised to sign, since applying another person signature without their authority is forgery whatever tool is used.

PDF Verified is a tool for preparing, signing, stamping and checking documents. It is not a law firm, a compliance service or a forensic examiner, and nothing here is legal, financial or compliance advice. Requirements differ by country, by document type and by the party asking, so check what applies to your document before you rely on it, and take advice where the document matters. You are responsible for the documents you create, sign and send, and for having the authority to do so: signing or stamping in somebody else name, or as an organisation you do not represent, is forgery whatever tool is used. To the extent the law allows, we accept no liability for how a document made with this tool is used or relied on. The full position is in our terms of service.

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