How to sign a PDF on a Mac

What your Mac needs

On a Mac, Attest runs in Safari or Chrome, with nothing to install. You sign with a passkey: a cryptographic key only you control, created for one website and unlocked with Touch ID, with your iPhone or iPad or, in Chrome with Google Password Manager, with the confirmation Chrome asks for. What unlocks it depends on your Mac and your browser:

• A Mac or Magic Keyboard with Touch ID. You confirm with your fingerprint. Apple says the sensor is at the top right of the keyboard, and you add a fingerprint in System Settings, under Touch ID & Password.
• A Mac without Touch ID. Use your iPhone or iPad: the passkey prompt lets you scan a QR code and confirm with Face ID on the phone, with Bluetooth turned on for both devices, Apple says.

Where the passkey is saved depends on your browser:

• Safari saves passkeys in iCloud Keychain, which must be set up on your Mac to create one. Each passkey there is "available on all your devices where you're signed in to the same Apple Account", Apple says, and iCloud Keychain is end-to-end encrypted with keys "not known to Apple".
• Chrome can save a passkey in Google Password Manager or in iCloud Keychain (macOS 13.5 or later), Google says. For Google Password Manager on a computer, Google's help says: "If this is your first passkey, you'll find a prompt to create a Google Password Manager PIN. This PIN will be requested every time you log in to a website where you have a passkey saved in Google Password Manager." When you use a passkey, Chrome "may require additional confirmation" by asking for your desktop password or PIN, your fingerprint or your Google Password Manager PIN, Google adds. An Attest signature uses the passkey the way a sign-in does, so the same confirmation appears.

Your fingerprint stays on your Mac. Apple says Touch ID data is "never stored on Apple servers" and "never backed up to iCloud or anywhere else". Touch ID only unlocks the passkey; the passkey signs a statement that names the exact document and everything you entered on it, and Attest receives that signature, never the passkey's secret.

Before you start

• The PDF on your Mac. In Mail, move the pointer over the message's header, click the Attach button, click the attachment's name, choose a location and click Save.
• 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 statement of work a client emailed you to sign and return. The video above records the signing part, from Sign a document yourself on.

1. In Safari or Chrome, go to attest.datahubz.com/sign and click Start free.
2. Type your email, click Email me a sign-in link, and open the link Attest sends you.
3. Set up your signing key, once. Click Security in the sidebar, under Settings, then click Set up with a passkey.
4. In Safari, place your finger on Touch ID. On a Mac without Touch ID, click Other Options and scan the QR code with your iPhone or iPad. Chrome shows its own prompt, where you choose where to save the passkey; the first time you save one in Google Password Manager, it asks you to create a Google Password Manager PIN.
5. 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 click Continue.
6. Open Documents and click Sign a document yourself.
7. Click Attach the document to be signed and choose your PDF. Its file name becomes the title, which you can change.
8. 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).
9. Click Next: place your signature, then click the page where you sign. For initials or a date, choose Initials or Date signed and click the page the same way. Drag a field to move it, or drag its corner to resize it.
10. Click Continue to sign. Attest opens the signing page.
11. Click Open and start signing. The PDF is decrypted in your browser; confirm the passkey prompt if one appears, because your passkey also unlocks your key.
12. Click your signature field. Type your full name, then pick a style or switch to Draw and sign with your trackpad or mouse, and click Adopt and sign here. Click the date field and it fills in the date.
13. Click Sign with your passkey and confirm with Touch ID (in Chrome with Google Password Manager, whatever Chrome asks for, such as your Google Password Manager PIN), or with your iPhone.
14. Click View and download the signed copy, then Download signed copy, and attach the PDF to your reply.

Send the copy once it 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 sent to you through Attest

A document someone sends you with Attest needs no account and costs you nothing. Click Review and sign in the email whose subject starts with "Signature requested", set up your passkey with Touch ID the first time (one prompt with most passkey providers), wait for the sender's browser to release the encrypted document (Attest emails you), then fill in the guided fields and click Sign with your passkey. How to sign a document someone sent you walks through every screen.

What your signed copy contains

Every party gets the same signed PDF: the signed pages, with a "Signed with Attest" stamp on each signature and a seal line at the foot of every page, a certificate of completion, the audit trail up to completion and a "Verify it yourself, without us" page, with the full evidence, the original document and a standalone verifier attached inside. Each stamp carries the document's verification code, the signing date and a QR code that opens its certificate.

Download signed copy saves the full sealed copy. Signed pages only saves just the document's own pages, stamps included, for a filing that must keep its page count. Both verify. Anyone can check them for free at attest.datahubz.com/verify, with no account, and the open-source verifier inside the PDF runs in any browser, even without Attest: it checks each signer's passkey signature, the original document, the pages you see and Attest's anchored record on Horizen, a public blockchain.

Attest or Preview

Preview can also put a signature on a PDF. Apple's steps: click the Show Markup Toolbar button, click the Sign button, create a signature with your trackpad, your Mac's camera or a nearby iPhone or iPad, then drag it where you want it. 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 quick 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 if one byte of the document or of your entries changes, verification fails.

What it costs

What you sign on your Mac	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.