How to sign a PDF on your iPhone, no app needed

Why you don't need an app or a printer

Signing on paper means print, sign, scan and send. Attest replaces all of it with two things your iPhone already has.

• A web browser. Attest runs in the browser, Safari on your iPhone, with nothing to install.
• A passkey. A passkey is a cryptographic key only you control, which your iPhone creates for one website and unlocks with Face ID, Touch ID or your passcode. Apple stores passkeys encrypted in iCloud Keychain, "where they aren't visible to anyone (including Apple)".

When you sign, your passkey signs a statement that names the exact document, by its fingerprint, and everything you entered on it. A fingerprint (a SHA-256 hash) is a short code calculated from the file's contents: change one character of the file and the fingerprint changes. That is what makes the signature yours and ties it to this document. Attest never sees your passkey's secret, and your face stays on your phone: Apple says Face ID data "doesn't leave your device".

Before you start

• The PDF in the Files app. If it came as an email attachment, open Mail, touch and hold the attachment, then choose Save to Files.
• A PDF of up to 8 MB, the document you want to sign.
• Your email address. Starting free needs nothing else, not even a credit card.

Sign a PDF someone emailed you

This is for a document you received outside Attest, such as a contract a client's lawyer emailed you to sign and send back. The video above records the signing part, from Sign a document yourself on, on a computer; on your phone, you tap where it clicks.

1. In Safari, go to attest.datahubz.com/sign and tap Start free.
2. Type your email, tap Email me a sign-in link, and open the link Attest sends you.
3. Set up your signing key, once. Open the menu, tap Security, then tap Set up with a passkey and confirm with Face ID.
4. Save the recovery phrase Attest shows you somewhere safe, such as your password manager. Attest can't recover it for you. Check I saved my recovery phrase. and tap Continue.
5. Open Documents and tap Sign a document yourself.
6. Tap Attach the document to be signed and choose your PDF from Files. Its file name becomes the title, which you can change.
7. Under Verification, keep Public certificate, or choose Private so that only you can see the certificate (anyone else who looks it up is told it exists and is private).
8. Tap Next: place your signature, then tap the page where you sign. If the document asks for initials or a date, choose Initials or Date signed and tap the page the same way.
9. Tap Continue to sign. Attest opens the signing page.
10. Tap Open and start signing. The PDF is decrypted on your iPhone.
11. Tap your signature field. Type your full name, then pick a style or switch to Draw and sign with your finger, and tap Adopt and sign here. Tap the date field and it fills in the date.
12. Tap Sign with your passkey and confirm with Face ID.
13. Tap View and download the signed copy, then Download signed copy, and attach the PDF to your reply.

Send the copy once its header reads "every party signed, sealed and anchored". If it says "anchoring now (preliminary copy)", close it and open it again a little later: on the Free plan the anchor is written within about 10 minutes, and on the Signing plan right after you sign. You can also open it later from Documents, with View the signed copy.

Sign a document someone sent you through Attest

When someone sends you a document with Attest, you need no account, no password and no plan, and it costs you nothing.

1. Open the email whose subject starts with "Signature requested" and tap Review and sign.
2. If this is your first document on Attest, tap Set up with a passkey and confirm with Face ID. With most passkey providers this takes one prompt.
3. The document is end-to-end encrypted, so the sender's browser releases it to your new key. Attest emails the sender, who releases it with their passkey. You can close the page: Attest emails you as soon as it's released, and the open page shows the document by itself. If you already have an Attest key, the document opens at once.
4. Tap Open and start signing. Attest guides you to each of your fields, and the Next button (for example "Next: initials") takes you to the next one.
5. Adopt your signature the first time you tap a signature, initials or full name field (type your full name, then pick a style or draw it), then fill in the other fields.
6. Tap Sign with your passkey and confirm with Face ID.

When the last person signs, every signer can view and download the same signed copy from their link, and Attest emails every party a link to the certificate. If you don't want to sign, tap Decline to sign. That closes the document for everyone and tells the sender.

What your signed copy contains

The signed PDF is the same file for every party, and it carries its own proof:

• the signed pages, with every signer's entries and each signature in a Signed with Attest stamp (the document's verification code, the signing date and a QR code that opens its certificate), and a seal line at the foot of every page with the same code and the link to verify it
• a certificate of completion, an audit trail of every step up to completion and a "Verify it yourself, without us" page, which explains how to check each step without Attest
• three files attached inside the PDF: the full evidence, the original document exactly as signed and a standalone verifier

Anyone can check it for free at attest.datahubz.com/verify, with no account. The open-source verifier inside the PDF runs in any browser, even without Attest, and checks each signer's passkey signature, the original document, the pages you see and Attest's anchored record on Horizen, a public blockchain. If a filing must keep its original page count, Pages only (Signed pages only on a wider screen) downloads just the document's pages, stamps included. It verifies too.

Attest or the iPhone's built-in Markup

Your iPhone can also add a drawn signature to a PDF: in Markup, tap Add Signature, sign your name with your finger, tap Done and drag it into place. That places an image of your signature on the page. Nothing in the image ties it to you or to this version of the document.

For a casual form, that may be all you need. When you may have to prove the signature later, to a client, a landlord or a lender, use Attest: the signature comes from your passkey, the signed state is anchored on a public blockchain, and change one byte of the document or of your entries and verification fails.

What it costs

What you sign on your iPhone	Cost
A document someone sends you through Attest	Free, on any plan. It uses none of your documents
A PDF you upload and sign yourself	One of your documents: 2 free in total, then the Signing plan, $5 a month for 20
A document you send to other people	One of your documents, the same way

The people who sign never pay, and paid plans can be cancelled any time.