How to sign a scanned document on iPhone

Someone handed you paper, or emailed you a scan of paper. Either way there’s no tidy PDF with a fillable signature field — just an image of a page with a line on it. The good news: an iPhone can handle the whole thing, and the built-in tools are free.

One thing worth knowing up front, because it explains everything below: a scan is a picture, not a document. There are no form fields inside it, nothing to click. Every tool — Apple’s, ours, anyone’s — is doing the same fundamental job: placing your signature on top of an image at the right spot. So the real question isn’t which tool can do it. It’s how much fiddling each one costs you.

Step 1: get a clean scan (skip if you already have one)

If you’re about to photograph the page — don’t. A flat photo of paper comes out shadowed, keystoned and grey, and it’s the single biggest reason returned documents get bounced back. iOS has a real document scanner built in, free:

Open Notes (or Files → tap ⋯ → Scan Documents).
Point at the page. It detects the edges and captures automatically.
It de-skews the page, crops it, and cleans up the contrast.
Share → Save to Files as a PDF.

Thirty seconds, and you get a straight, high-contrast PDF instead of a photo of your kitchen table. If your scan came in by email or already lives in Files, skip ahead — you’re set.

Step 2, option A: iOS Markup (free, already installed)

Once the scan is a PDF in Files or an email attachment:

Open the PDF and tap the pencil (Markup) icon.
Tap + → Signature — draw one with your finger, or reuse a saved one.
Drag it onto the signature line and resize with the handles.
Need the date too? + → Text, type it, drag it into place.
Tap Done, then share the signed copy back.

Where this is genuinely enough: a one-off signature on a single page. It’s free, it’s already on your phone, and if that’s your situation you can stop reading — you don’t need an app for this.

Where it starts to hurt, honestly: finger-drawing a signature you’re happy with on glass takes a few attempts, and Markup forgets the fiddly bits — dates and initials are manual text boxes you nudge into position each time. On a multi-page scan that wants initials on every page, that adds up fast. And Markup’s signature sits on the page as an annotation rather than being merged into it.

Markup can also sign a photo directly from Photos, without the scanner step — but you’ll be placing a signature on a crooked, shadowed image, and the result looks like it. Scan first. If the paper is already gone and a photo is all you have, adding a signature to a photo of a document on iPhone covers that case, including how to get a PDF back instead of a JPEG.

Step 2, option B: a signature app (when scans keep coming)

If paper is a recurring feature of your life — a landlord, a contractor, a parent of a school-age child — the setup cost stops being worth paying repeatedly:

Open Signed and import the scan straight from Photos or Files.
Tap where the signature goes. Your saved signature drops in at the right size.
Initials and today’s date are one tap each — on every page, if the document wants that.
Tap Finish for a flattened PDF — the signature is merged into the page, not floating on top of it — and share it back.

You create the signature once, properly: draw it large, type your name in a real handwriting style, or let AI generate one from your name. Every scan after that is the same four taps. If you’d rather see what a decent signature looks like before committing to anything, the free signature generator runs in your browser — no signup, nothing uploaded.

On privacy: scans are exactly the documents you’d rather not hand to a server — they’re often IDs, bank letters, signed agreements. Signed is local-first: the scan and the signature stay on your phone, and there’s no cloud copy to worry about.

Which one should you use?

One page, once → Notes scanner + Markup. Free and completely fine.
Regularly, or the document wants initials on every page → an app saves you the fiddling from the first document onward.
It’s a high-stakes legal document → the tool is the easy part. A signature image on a scan may not be the whole requirement — check what’s actually needed for that document type before you send it.

A few things that get scans rejected

Sending a photo instead of a scan. Use the scanner. It’s free and it takes seconds.
Signing at the wrong size. Your signature should sit on the line, not straddle two paragraphs.
Missing the date or the initials. Scanned forms almost always want more than the signature — check every page before sending.
Sending the individual page images rather than one PDF. One file, in page order.