How to Sign a PDF on iPhone (Step by Step)

If someone just emailed you a contract, an onboarding form or a permission slip, you probably want to know how to sign a PDF on iPhone without printing, scanning or hunting for a laptop. The good news is that your iPhone can already do it. This guide walks through the built-in options step by step, covers the small details that trip people up (saving, resizing, sending the right copy back), and explains when it makes more sense to use an e-signature tool instead of a drawn-on signature.

What you need before you start

You don't need to buy anything to add your own signature to a PDF on an iPhone. Before you begin, check three things:

The PDF is on your phone. If it arrived as an email attachment, a text or a download in Safari, you can open it directly. If you're prompted, open it in the Files app and tap Save so you're working on a copy you control.
You know where the signature goes. Skim the whole document first. Many forms have a signature line, a date line and initials on several pages.
You know how to send it back. Decide whether the sender wants it by reply email, upload to a portal or a shared folder. That decides which "Share" option you'll pick at the end.

Menus can look a little different depending on your iOS version and the app you open the file in, but the basic flow is the same everywhere: open the PDF, open the markup or form tools, add a signature, place it, then save or share.

How to sign a PDF on iPhone with the Files app

The Files app is the most reliable place to sign, because the signed copy stays saved on your phone. According to Apple's guide to filling out forms and signing documents on iPhone, the steps look like this:

Open the PDF. If it came from Mail or Messages, tap the attachment and, if asked, save it to Files.
Tap the markup or form button (a pen-tip icon) to open the editing tools.
Tap any blank fields and type your information. If a prompt offers to fill several fields at once with your saved contact details, review them before you accept.
Tap the plus (+) button, then tap Add Signature.
Sign your name with your finger and tap Done. Rotating your phone sideways gives you more room to write.
Drag the signature onto the signature line. Use the blue dots around its box to make it bigger or smaller.
Tap Done to save the signed PDF.

Your iPhone remembers the signature, so next time you only need to tap it instead of drawing it again. You can also save more than one, such as a full signature and a set of initials.

Signing straight from an email in Mail

If the PDF is attached to an email in Apple Mail, you can tap the attachment, open the markup tools and follow the same steps. When you tap Done, Mail usually offers to reply with the marked-up copy attached. That's handy, but double-check that the reply is going to the right address and that the attachment is the signed version, not the original.

Using the Preview app

Newer versions of iOS also include a Preview app for PDFs. Apple's Preview instructions are short: open the PDF form in Preview, tap the edit button, tap a field to type, and use the add button to insert a signature or a text box. If you already use Preview on a Mac, this will feel familiar.

Common problems and quick fixes

Most frustration with signing on a phone comes from a handful of small issues. Here's how to handle them.

Problem	What to try
No markup button appears	Save the PDF to Files first, then open it from there.
The signature looks shaky	Rotate the phone sideways, sign slower, or tap Clear and redo it.
The signature is too big for the line	Drag a corner dot inward and zoom in on the page to place it precisely.
You can't type in a field	The PDF may not have form fields. Use Add Text Form Box and drag it into place.
The sender says nothing changed	You may have shared the original. Reopen the saved copy in Files and share that one.

One more tip: before you send, zoom out and scroll through every page. It's easy to sign page three and forget the initials on page five.

When a drawn signature isn't enough

Drawing your name on a PDF works well when you're the only person signing and the other side just needs a copy back. It gets clumsy in a few situations:

You're the one collecting signatures. If you run a small business and need clients, tenants or new hires to sign, emailing a PDF and hoping they figure out markup tools leads to back-and-forth, missing initials and files that come back as photos.
Several people need to sign the same document. Passing one PDF from inbox to inbox is slow, and it's hard to tell which copy is the latest.
You need to know where things stand. A drawn signature doesn't tell you when someone opened the document or whether they've finished.
You send the same form again and again. Re-marking the same signature lines every time wastes time.

Whether a particular signature method is acceptable for a specific contract depends on the document and where you are. If that question matters for your situation, check with your attorney.

Sending a PDF for signature from your iPhone with ReadyInk

When you need other people to sign, an e-signature tool handles the parts that markup can't. With ReadyInk you can send documents for signature from your phone's browser, and the people signing don't need an account. They open a link, review the document and sign.

Here's how it works in practice:

Upload the PDF. ReadyInk's AI places every field on the document for you, so you don't have to drag tiny boxes around on a small screen.
Review before sending. You check the fields and signers, adjust anything you want, and only then send.
Track and remind. You can see where each document stands and send reminders. Reminders don't use tokens.
Get the finished copy. You can send copies to extra recipients, such as a business partner or bookkeeper, without using tokens.

If you send the same form often, turn it into a reusable template with signer roles, fields and intake questions. Our guide on turning a PDF into a reusable e-signature template walks through that setup. And if you only need to put your own signature on a file from a computer, see our page on how to sign a PDF online.

What it costs

Signing a PDF yourself on ReadyInk is free: choose Just me when you upload, let AI place the fields, sign and download. Sending to other people uses tokens instead of a required monthly subscription. One token covers one signer on one document. Packs start at $10 for 20 tokens, and the Volume pack is $100 for 400 tokens, which works out to $0.25 each. Purchased tokens never expire, and failed sends are refunded. Teams can choose the Team plan at $15/month for 3 users with 30 shared monthly tokens. More details are on our e-signature for small business page.

Frequently asked questions

Do I need an app to sign a PDF on iPhone?

No. The Files app, Mail and Preview include signature tools, so you can sign a PDF on iPhone with what's already installed. Third-party apps are only needed if you want extra features like sending to other signers or tracking status.

Can I save my signature for next time?

Yes. After you draw a signature, your iPhone saves it so you can tap it into place on future documents. You can save several, such as a full name and initials, and delete any you no longer want.

How do I get someone else to sign a PDF from my iPhone?

You can email the PDF and ask them to use their own phone's markup tools, but that's hard to track. A simpler option is to upload the PDF to ReadyInk, review the fields, and send a signing link. The signer doesn't need an account, and you can send reminders without using tokens.

Signing your own PDF on an iPhone takes about a minute once you know where the tools are. When you need other people to sign, and you want fields placed for you, reminders and a clear status for every document, try ReadyInk at app.readyink.ai and send your first document from your phone.