The simplest way to fill a PDF on iPhone

You can fill out most PDFs directly on your iPhone using the built-in Books app or Mail app, without downloading a separate tool. If the PDF has form fields — boxes, checkboxes, or signature lines — your iPhone recognizes them and lets you type or tap to complete them. The filled PDF saves to your phone, and you can email it or share it with whoever needs it.

If the PDF is a scanned image with no form fields, or if you need to mark it up with notes and drawings, you'll use the Markup tools built into iOS instead. Both routes work on any iPhone running iOS 14 or later, and neither costs money.

Key Takeaways

  • PDFs with form fields fill fastest in the Books app — open the file, tap a field, and type your answer.
  • If you receive a PDF by email, you can fill it directly in Mail without saving it first.
  • Scanned PDFs without form fields need the Markup tool, which lets you draw, type, and sign anywhere on the page.
  • Your filled PDF saves automatically, and you can send it back by email or share it through any app that accepts files.
  • If your iPhone runs iOS 14 or earlier, update to access the full set of PDF tools.

Filling a PDF with form fields in the Books app

Open the Books app on your iPhone and find the PDF you want to fill. If the file is on your phone, it's already there. If it's in your email or cloud storage, read it first by tapping and holding the file, then selecting "Save to Books" or "Open in Books."

Once the PDF is open in Books, look for the form fields — they appear as empty boxes, lines, or checkboxes. Tap any field to set up it. Your keyboard appears, and you type your answer directly into that field. For checkboxes, tap once to mark them. For dropdown menus, tap the field and select from the list that appears.

When you finish filling all the fields, the app saves your work automatically. You don't need to press a save button. To send the completed PDF, tap the share icon (three dots or an arrow), choose "Share PDF," and select Mail, Messages, or another app to send it.

Filling a PDF that arrives in your email

If someone sends you a PDF to fill out, you can complete it without leaving the Mail app. Open the email and tap the PDF attachment to preview it. If the PDF has form fields, you'll see a button that says "Markup" or a pencil icon in the top right corner.

Tap that button to enter editing mode. You can now tap form fields and type your answers, just as you would in the Books app. When you're done, tap "Done" and then tap the reply arrow to send the filled PDF back to the sender. Mail automatically attaches your completed version to your reply.

Using Markup tools for PDFs without form fields

If your PDF is a scanned document or an image without clickable form fields, use the Markup tool instead. Open the PDF in any app — Books, Mail, Files, or Photos — and tap the Markup button (usually a pencil in a circle icon).

The Markup toolbar appears at the bottom of your screen with several options. The pen tool lets you write or draw anywhere on the page. The text tool (marked with an "A") lets you type text boxes that you can place anywhere. The signature tool lets you sign your name with your finger. The magnifying glass lets you zoom in on a specific area to work more precisely.

Choose your tool, then tap or draw on the PDF where you need to add information. You can undo a stroke by tapping the arrow icon. When you finish, tap "Done" to save your changes. The marked-up PDF is now ready to share or email.

Adding your signature to a PDF

To sign a PDF on your iPhone, open it in any app and tap the Markup button. In the Markup toolbar, look for the signature tool — it usually shows a pen or signature icon. Tap it, then tap "Add Signature" if this is your first time signing.

You'll be asked to sign your name on the screen with your finger. Sign naturally, as you would on paper. When you're happy with how it looks, tap "Done." Your signature is now saved to your phone. The next time you need to sign a PDF, you can use this saved signature instead of drawing it again.

To place your signature on the PDF, tap the spot where it should go. You can resize it by pinching and dragging the corners. When the signature is positioned correctly, tap outside it to lock it in place, then tap "Done" to save the PDF.

Saving and sharing your completed PDF

After you fill out or mark up a PDF, your changes save automatically to the file. The original PDF is replaced with your completed version — there's no separate "save" step. If you want to keep both the original and your filled version, make a copy before you start editing.

To share your completed PDF, open it and tap the share icon. Choose Mail to email it, Messages to text it, or any other app that accepts file attachments. You can also save it to cloud storage like iCloud Drive or Google Drive by tapping "Save to Files" and selecting your storage location.

Troubleshooting common problems

If the PDF won't let you type in a field, the form may not have actual form fields — it might be a scanned image instead. Switch to the Markup tool and use the text tool to type your answer anywhere on the page.

If the Markup button doesn't appear, make sure you're running iOS 14 or later. Go to Settings, tap General, then Software Update to check your version. If you're on an older version, update your phone first.

If your filled PDF looks different when you open it on a computer, the form may use fonts or formatting that don't display the same way on different devices. This is normal and doesn't affect the information you entered. The content is still there and readable.

Frequently Asked Questions

Can I fill a PDF on iPhone without downloading an app?

Yes. The Books app, Mail app, and Markup tool are built into iOS, so you don't need to read anything. Open your PDF in any of these apps and start filling it out.

What's the difference between form fields and Markup?

Form fields are clickable boxes that the PDF creator set up for you to fill in — you tap them and type. Markup is a freehand tool for scanned documents or images where you can write, draw, or type anywhere on the page.

Does my signature on an iPhone PDF count as a legal signature?

That depends on what the document is for and who's asking for it. Many organizations accept digital signatures on contracts and forms. If you're unsure, ask the person or organization requesting the signature whether a digital signature is acceptable for their purposes.

Can I edit a PDF I already filled out?

Yes. Open the PDF again, tap Markup, and make your changes. You can edit form fields by tapping them again, or use the Markup tools to cross out or add information.

What happens if I accidentally close the PDF before saving?

Your changes save automatically as you work, so closing the app won't erase what you've done. When you open the PDF again, your filled information will still be there.