How to sign a PDF in your browser with Sign

Sign places your signature, initials, text, and dates on any PDF and downloads the signed copy — the document itself never leaves your browser.

Before you start

• Your PDF stays on your device. The signature is stamped locally in the browser. The only exceptions are the optional network features — “Send for signature” and “Sign on phone” (the file travels as encrypted ciphertext), “Co-sign live” (the PDF flows peer-to-peer to your co-signer, never through AttachKit's server), and “Review with AI” (document text goes to the AI) — and the privacy badge next to the file name labels the network step whenever one happens.
• Files up to 100 MB. Larger drops are rejected to keep your browser responsive; split big files with Pages first.
• Free plan: 15 signed PDFs a month. A counter shows “X of 15 free signs used this month.” During the private beta, signing in makes signing unlimited and free.
• Password-protected PDFs can't be signed until the password is removed — use Unlock if you know it. PDFs that only have an owner/permissions password are decrypted automatically on your device when you drop them.

Steps

1. Open Sign and drop your PDF — or click Try with a sample to see how it works first.
2. Build your signature in the Your signature panel. Use the Draw tab to sign with your mouse or finger, or the Type tab to type your name and pick a handwriting style (Caveat, Dancing Script, or Great Vibes). Signatures you build are saved for reuse — in this browser when you're not signed in, or in your account when you are; an optional vault passphrase encrypts the browser-stored ones.
3. Pick a tool in the bar above the document — Signature, Initials, Text, or Date — then tap or click the PDF where you want it. Drag a placed item to reposition it; select it to resize or delete it. Initials are built in the collapsed + Add initials (optional) panel in the sidebar.
4. Optionally open Output options in the sidebar — the choices are listed in the table after these steps.
5. Click Download signed PDF. The signed copy downloads as yourfile-signed.pdf. On the free plan it carries a small “Signed with AttachKit” footer line; Pro removes it.
6. If you signed with a passkey, the success message offers Verify — it opens Verify with the freshly signed file so you can confirm the proof end to end.

Output options

The Max rows are paid-tier features — during the private beta, signing in unlocks them for free. Passkey signing needs a passkey registered at /account/signing-keys.

Other ways to sign

The Share & advanced menu holds five more flows:

• Sign on phone — shows a QR code; scan it with your phone to keep signing on a touchscreen.
• Send for signature — send a link so someone else signs in their own browser. You don't have to place anything first; the recipient adds their own signature.
• Sign multiple — applies your current placements to a whole batch of PDFs; one passkey confirmation covers the batch.
• Multi-party — witness and co-signer ceremonies using multiple passkeys on this device; a Max feature.
• Co-sign live — a real-time co-sign room over a direct WebRTC connection, a Pro feature (free during the private beta).

There's also Review with AI, which flags risky contract clauses (non-compete, indemnification, auto-renewal, and similar) before you sign. This one sends the document text to the AI, and the badge by the file name says so when you use it.

Saving progress

Placed fields aren't autosaved. Save draft encrypts the PDF, your signature, and the placements into this browser; resume later from the Resume a draft list on the Sign home screen. The tab also warns you before closing with unsaved placements, and Start over asks for confirmation before discarding placed fields.

Result

You get a signed PDF on your device, named after the original with -signed appended. With the audit-trail page and passkey signature turned on, anyone can check at Verify that the signature is genuine and the file hasn't been altered since — no account needed.

Related

• Verify — check a signed PDF's passkey proof and edit history
• Fill — fill the form fields before you sign
• Unlock — remove a password you know so the PDF can be signed
• If a button is greyed out or the file won't load, see the Sign troubleshooting article.