How to Sign a PDF Document on Your iPhone Using the Files App

When someone emails you a contract or a permission slip while you are away from your desk, the thought of finding a printer, physically signing the document, scanning it, and emailing it back from your phone seems impossible. However, Apple has built a sophisticated digital signature tool directly into the native iOS Files app, allowing you to sign documents on the go using just your finger.

This guide explains how to save a PDF from an email, apply your signature, and send it back—all entirely from your iPhone.

Step 1: Save the PDF to the Files App

While you can sometimes sign documents directly inside the Mail app, saving the document to the Files app first provides a much more stable and reliable experience.

1. Open the email containing the PDF attachment.
2. Tap the PDF icon to preview the document.
3. Tap the Share icon (a square with an arrow pointing upward) in the top-right corner.
4. Scroll down the menu and tap Save to Files.
5. Choose a location (e.g., “On My iPhone” or an iCloud Drive folder) and tap Save in the top-right corner.

Step 2: Sign the Document

1. Close your email and open the native Files app on your iPhone.
2. Navigate to the folder where you just saved the PDF and tap the file to open it.
3. In the bottom-right corner of the screen, tap the Markup icon (it looks like a small pen tip).
4. At the bottom of the screen, a row of coloured pens will appear. Tap the + (Plus) icon located in the very bottom-right corner.
5. Select Signature from the pop-up menu.

If you have ever signed a document on your Mac (which shares your iCloud account), your signature will already be listed here. If not, you will be prompted to create one:

• Turn your iPhone horizontally (landscape mode).
• Use your index finger to write your signature on the glass screen.
• Tap Done.

Step 3: Position the Signature

Your signature will drop right into the middle of the document.

1. Move: Press and hold the middle of the signature, then drag it to the correct signature line on the document.
2. Resize: Grab one of the four blue dots on the corners of the signature box and drag inward or outward to shrink or enlarge the text so it fits perfectly on the line.
3. Once you are satisfied, tap Done in the top-left corner of the screen.

The signature is now permanently flattened into the PDF file. You can simply tap the Share icon again to instantly attach the signed document to an email and send it back.