How to sign a PDF on an iPhone

By Grace Whitfield, office-operations consultant · Updated November 1, 2026

Someone has emailed you a PDF to "sign and return", and you are nowhere near a printer. An iPhone can do the whole job: open the PDF, sign it with your finger, fill in the date, and send it back. Here are three free ways, from the most flexible to the quickest, and what each one is good at.

Method 1: FormFlow in Safari (fill and sign, multiple signers)

Use this when the document also needs filling in, when you need initials on several pages, or when two people need to sign on the same phone.

1. Save the PDF to Files. In Mail, touch and hold the attachment, then choose Save to Files. From a website, open the PDF, tap the Share button and choose Save to Files.
2. Open Sign PDF in Safari and tap Choose PDF. Pick Browse and select the file.
3. Tap Signature. Draw with your finger on the pad. Turning the phone sideways gives you a longer pad, which makes a more natural signature. You can also type your name in a handwriting font, or upload a photo of your signature on white paper — FormFlow removes the background.
4. Drag the signature into place with one finger and resize it with the pink corner dot. Add Initials and Date the same way.
5. Tap Finish, then Download. The signed PDF is saved to Files › Downloads. Open it and use Share to send it by Mail or Messages.

Everything happens inside Safari on your phone; the PDF is not uploaded anywhere. You can see exactly how that works on how FormFlow keeps files on your device.

Method 2: Markup in the Files app

Good for a quick signature on a document you already have in Files.

1. Open the PDF in the Files app.
2. Tap the Markup button (a pen tip in a circle).
3. Tap the + button and choose Add Signature. Create a signature the first time, or pick a saved one.
4. Drag and resize the signature, then tap Done. Files saves the change into the PDF.

Markup is quick, but fillable form fields are not always handled well — text typed into Markup boxes floats on top of the page rather than going into the form's fields. For forms, Method 1 is more reliable.

Method 3: Straight from a Mail attachment

1. Open the email and tap the PDF attachment.
2. Tap the Markup button, then + › Add Signature.
3. Place the signature and tap Done. Mail offers to reply with the marked-up PDF attached.

This is the fastest route when you only need a single signature and want to reply to the same email.

Tips for a signature that looks right

• Sign slowly and big. A signature drawn large and then scaled down looks smoother than a tiny scribble.
• Use the right ink. Black or dark blue reads best when the document is printed or faxed later.
• Check the date format. US forms usually expect mm/dd/yyyy.
• Flatten before sending if the PDF had form fields, so answers display the same in every app. FormFlow's Sign tool has a "Flatten form fields" option.

Does a finger-drawn signature count?

For most everyday documents in the US, an electronic signature has the same legal effect as ink, under the federal ESIGN Act and state UETA laws — but there are exceptions, such as wills. Our plain-English guide, are electronic signatures legal in the US?, explains the rules and their limits.

Signing a paper document instead

If the document arrived on paper, sign it in ink, then turn it into a clean PDF with Scan to PDF — see how to scan documents with your phone.