Guides
How to Sign a PDF on Your Phone: A Practical Guide to Mobile Signatures
Updated 24 August 2026 · 7 min read
Learn how to sign a PDF on your phone in under a minute: draw or reuse a signature, place it accurately, add the date, flatten the file, and keep the document private.
How do you sign a PDF on your phone?
Open the PDF in a mobile PDF editor, choose the signature tool, draw your signature with a finger or stylus (or reuse a saved one), drag it onto the signature line and resize it, add the date if needed, then export a flattened copy. In an offline app like Paperly PDF the signed document never leaves your phone.
Key takeaways
- Signing on a phone takes under a minute: draw once, save the signature, reuse it forever.
- A stylus or finger drawing beats a typed script font — recipients recognise it as a real signature.
- Add the date next to the signature; many agreements are only complete with one.
- Flatten the exported PDF so the signature cannot be dragged off or deleted.
- Simple electronic signatures are broadly enforceable under ESIGN (US) and eIDAS (EU) for everyday agreements.
Sign a PDF on your phone in six steps
- Open the PDF in your mobile PDF editor — straight from the email attachment, Files or Drive.
- Tap the signature tool and choose to draw a new signature or reuse a saved one.
- Draw with a finger or stylus on the signing canvas. Redraw until it looks like your normal hand.
- Place it on the signature line, then drag the corner handles to size it so it sits on the line, not above it.
- Add the date — and initials on other pages if the agreement asks for them.
- Export a flattened copy and send it back.
Three kinds of electronic signature
| Type | What it is | Typical use |
|---|---|---|
| Simple (SES) | A drawn, typed or image signature applied to a document | NDAs, rental agreements, consent forms, invoices, school and HR paperwork |
| Advanced (AES) | Cryptographically linked to the signer and tamper-evident | Higher-value B2B contracts, regulated onboarding |
| Qualified (QES) | AES issued via a qualified trust service provider with verified identity | Legally mandated cases in the EU, such as certain notarial acts |
The overwhelming majority of documents an individual signs in a year are in the first row. That is what a phone signature is for, and why the process should take seconds rather than an account signup.
Drawing a signature that looks right
A finger drawing at 100% zoom tends to look shaky and oversized. Two changes fix almost every bad mobile signature:
- Draw big, place small. Sign across the full width of the canvas, then scale the result down onto the line. Shrinking hides tremor; enlarging exposes it.
- Sign in one continuous motion. Lifting mid-name produces disconnected strokes that read as a drawing rather than a signature.
A stylus helps, but is not required. Avoid typed script fonts for anything that matters — they are visibly generic and easy to reproduce.
Placing, dating and initialling
Zoom to at least 200% before you drop the signature so the baseline sits on the printed line rather than floating over the text beneath it. Then check the rest of the document: many agreements need initials in a page corner, a printed name beneath the signature, or a date in DD/MM/YYYY or MM/DD/YYYY form depending on the country of the counterparty.
If several people must sign, send the exported file onward rather than re-signing a scan of a scan — every scan cycle degrades legibility.
Flatten before you send
An unflattened signature is an annotation object. In another PDF app the recipient can select it, move it, or delete it — and some readers will not display it at all. Flattening on export merges it into the page so the document looks and behaves the same everywhere.
Read more about the export step in our guide to editing PDFs on Android.
Are phone signatures legally valid?
For ordinary agreements, yes in most jurisdictions. The US ESIGN Act and EU eIDAS Regulation 910/2014 both provide that a signature is not invalid merely because it is electronic. What matters is intent to sign, consent to electronic form, and a record that can be retained.
Exceptions exist — wills, certain property transfers, adoption and some court documents may require wet ink or a qualified signature. For high-stakes documents, confirm the requirement with the counterparty or a lawyer before signing on a phone. This article is general information, not legal advice.
Keeping your signature private
Your signature image is biometric-adjacent personal data: combined with a scanned ID it is exactly what document fraud needs. Online signing portals store both the signature and the document on their infrastructure, often with retention measured in months.
Paperly PDF stores the saved signature only in the app's private storage on your device and performs signing offline, so no copy is transmitted anywhere. See why on-device editing is safer than online tools and our privacy policy.
Frequently asked questions
How do I sign a PDF on my Android phone?
Open the PDF in a mobile PDF editor, tap the signature tool, draw your signature with a finger or stylus, drag it onto the signature line and resize it, add the date, then export a flattened copy of the document.
Is a signature drawn on a phone legally binding?
In most everyday cases yes. The US ESIGN Act and EU eIDAS regulation both recognise simple electronic signatures for ordinary contracts, provided the signer intended to sign and consented to electronic form. Certain documents — wills, some property deeds and certain court filings — still require wet ink or a qualified signature. Check local rules for high-stakes documents.
Can I reuse the same signature on other documents?
Yes. Save the drawing once and place it on any future PDF in two taps. Keep it stored on the device rather than in a cloud account.
Do I need an account or subscription to sign a PDF?
No. Paperly PDF signs and exports without an account, without a watermark and without an internet connection.
How do I stop someone editing my signature after I send the file?
Flatten the document on export. Flattening merges the signature into the page content so it cannot be selected, moved or deleted in a normal PDF reader.
Is it safe to upload a contract to an online signing site?
It means handing a third party a copy of the contract and an image of your signature. For sensitive agreements, sign on-device instead so neither ever leaves your phone.