How to sign a PDF on iPhone or iPad

Your iPhone can already do this, for free, and most people never find the button. Here is the built-in way first, then the two situations where it stops being enough.

Method 1 — Apple Markup (free, already on your phone)

Markup is built into iOS and iPadOS and works from Mail, Messages, Files and anywhere else a PDF appears.

1. Open the PDF — tap the attachment in Mail, or the file in Files.
2. Tap the Markup button (a pen tip) in the top right.
3. Tap the + button in the bottom right and choose Signature.
4. Draw your signature with a finger or Apple Pencil, then tap Done. It is saved, so you never draw it twice.
5. Drag it into place; drag a corner handle to resize it.
6. Tap Done. From Mail, choose Reply With Attachment and the signed document goes straight back to the sender.

Where Markup runs out: adding text is possible but fiddly — the boxes are hard to place accurately with a fingertip, and lining twelve of them up on a form is unpleasant. And if the PDF has real interactive form fields, Markup ignores them; you end up drawing text boxes on top of fields that were designed to be typed into.

Method 2 — the Files app

Same Markup tools, reached differently: open Files, tap the PDF, tap the Markup button, and proceed as above. Useful when the document is already saved rather than sitting in an email. Tap Share when you are finished to send it on.

Method 3 — a dedicated app, when Markup is not enough

Worth it in two specific situations: the document is a real form with interactive fields, or you sign things often enough that Markup's rough edges have become a weekly irritation.

AddToPDF, ours, detects existing form fields so you type into them with a proper keyboard instead of positioning boxes by hand; it lets you compose text first and then place it, which is far easier with a thumb than typing directly onto a zoomed page; it scans paper with the camera when what you have been sent is a physical form; and it appears in the share sheet, so a PDF from any app opens in it in one tap and goes back out the same way. It is a one-time purchase covering iPhone, iPad and Mac.

PDF Expert is the more powerful app on iOS — it edits existing PDF text and does OCR, which ours does not — and it is sold by subscription for iPhone, iPad and Mac. PDFgear has a free iOS app. If money is the deciding factor, start there.

AddToPDF — the app we make

A deliberately small PDF editor for Mac, iPhone and iPad: add text, sign, fill forms, organise pages. Fully offline, no account, one-time purchase covering all three devices. It does not edit existing body text or do OCR.

Download on the App Store

Why every iOS app makes you "share" the file back

This confuses people, so it is worth a paragraph. Since iOS 17, an app generally cannot edit a document in place where it lives in another app's storage. What happens instead is that a copy is handed to the app you picked; you edit that copy; you send the finished file back out through the share sheet.

So the pattern on iOS is always receive → edit → share back, not "open and save". Every PDF app on the platform works this way, including the expensive ones. If you were expecting your edits to appear automatically in the original file in iCloud Drive, they will not — send the finished copy where it needs to go.

Is a finger-drawn signature good enough?

For everyday agreements — a rental form, a school permission slip, a freelance contract, an NDA — an electronic signature of this kind is how the overwhelming majority of documents are signed, and is generally valid.

What it is not is a cryptographic digital signature: one backed by a certificate that proves who signed and detects later tampering. Certain regulated transactions require that, and some organisations mandate a particular signing platform. The practical rule: for ordinary business, draw and send; if the document is high-stakes or a regulator is involved, ask the other party what they require before signing anything.

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