Most signatures now happen on phones. The document arrives by email or message, the person reads it on the bus or between meetings, and signs with a finger. If the experience is good, it takes a minute. This guide covers the three situations you are likely to be in: signing something someone sent you, signing a PDF you already have, and sending a document for someone else to sign, all from your phone.
1. Signing a link someone sent you
This is the most common case. A business sends you a contract, a lease or an offer letter through an e-signature service, and you receive an email (sometimes a WhatsApp message or a text) with a link.
You do not need an app or an account. The link opens in your phone's browser. Here is what that looks like when someone sends you a document with Salsox:
- Open the link. You see the document's title, who sent it and what you are asked to do.
- Agree to sign electronically. A checkbox confirms you are happy to sign and receive the document electronically. This consent is part of what makes the signature hold up later.
- Go through the fields. The page takes you from one field to the next. For the signature you can draw it with your finger, type your name (shown in a signature style) or upload an image.
- Finish. When everyone has signed, you can download your copy straight away, and it is emailed to you as well.
A few tips make it smoother:
- Turn the phone sideways for a wider canvas if you are drawing.
- Zoom with two fingers to read small print; the fields stay where they are.
- Don't forward your link. It signs as you. If someone else should sign, ask the sender to add them.
- Check the sender. If a signing request is unexpected, contact the sender through a channel you already use before opening it.
2. Signing a PDF you already have
Sometimes you have the PDF yourself, a form to return or a document to sign and email back. You have three options.
In your browser (iPhone and Android)
A browser-based tool works the same on any phone. With the free Sign PDF tool, you choose the file, draw or type your signature, place it on the page and download the signed copy. The file is processed on your phone and never uploaded. If the PDF has form fields to fill first, Fill and sign PDF handles both.
iPhone: Markup
iPhones have a signature tool built in:
- Open the PDF in the Files app, or tap the attachment in Mail.
- Tap the Markup button (a pen tip).
- Tap +, then Add Signature, and draw your signature.
- Drag it into place, resize it, and tap Done.
The signature is saved for next time, which is convenient and also a reason to keep your phone locked.
Android: a PDF app
Android phones vary by manufacturer, so the browser route is the most dependable. Many people also use a PDF app with a fill-and-sign feature, such as Adobe Acrobat Reader: open the PDF, choose Fill & Sign, create your signature and tap where it should go.
One limitation applies to all three: signing your own copy shows that you signed, but not when, or that nobody changed the file afterwards. For a contract between two parties, an e-signature service that records each step is better evidence. The complete guide to signing a PDF explains the trade-offs.
3. Sending a document for signature from your phone
You can also be the sender. With Salsox on your phone's browser:
- Open Quick Send and choose the PDF from your files, email attachments or cloud storage.
- Type the email address of each signer.
- Tap Send. A signature and date field are placed for each signer automatically.
Each signer gets an email with their own link. From the document's page you can also share each link by WhatsApp or SMS, often the fastest way to reach someone who lives on their phone. The page shows who has opened and signed, and unsigned recipients are reminded automatically every three days.
If you would rather write your own message than rely on the default, our guide to requesting an e-signature by email has wording that works.
Is a phone signature legally valid?
In most countries, yes. Electronic signature laws such as the US ESIGN Act, the EU's eIDAS Regulation and the UK's Electronic Communications Act do not distinguish between devices: a signature drawn on a phone is treated like one made with a mouse. What matters is intent, consent and a record that links the signer to the document. Some documents, such as wills, are excluded from e-signing in many places whatever the device. See are electronic signatures legally binding? for the details.
Start on your phone
You can sign a PDF now with the free Sign PDF tool, no account needed. To send documents for signature, create a free account: the free plan sends 3 documents a month, and the pricing page lists the paid plans.
Frequently asked questions
Can I sign a document on my phone without an app?
Yes. A signing link someone sends you opens in your phone's browser, and browser-based tools can sign a PDF you already have. Nothing needs installing.
How do I sign a PDF on an iPhone?
Open the PDF in the Files app or from Mail, tap the Markup button, then the plus button and Add Signature. Draw your signature, place it and tap Done. A browser tool or a signing link works too.
How do I sign a PDF on Android?
Use a browser-based signing tool, which works the same on any Android phone, or a PDF app with a fill-and-sign feature such as Adobe Acrobat Reader.
Is a signature made on a phone legally valid?
In most countries, yes: the law does not care which device you used. What matters is that you intended to sign and that there is a record linking you to the document.