How to sign a PDF on Android

Four steps, about a minute, without sending your document to a stranger's server.

Someone has sent you a PDF and is waiting for it back with your signature on it. You are on your phone. Here is how to do it properly, and what to watch out for with the usual alternatives.

The quick way

1. Open the PDF in PDF SignerTap Import PDF and pick the file. If the document arrived by Gmail, WhatsApp or Drive, you can also open it from there and choose PDF Signer.
2. Make your signature, onceDraw it with your finger, type your name and pick a handwriting style, or photograph a signature you wrote on paper. It is saved on the phone, so you never do this step twice.
3. Drag it onto the pageTap Signature, then move it where it belongs and pull the corner to size it. Add the date, your initials or a note the same way if the form needs them.
4. Save and send it backTap Save Signed PDF, give the file a name, and choose to keep it, put it in a folder, or share it straight back to whoever asked.

Why not just use a website?

Search for "sign pdf" and you will land on a site that asks you to upload the document. That works, and for a menu or a leaflet it is fine. For a contract, an NDA, a payslip or a passport form it means handing a private document to a company you have never dealt with, usually followed by an account, a daily limit, and a subscription page on the third file. Some of them stamp a watermark on the result.

An app on the phone avoids all of that, because the document never has to go anywhere. PDF Signer works with your data switched off, which is the simplest possible proof that nothing is being uploaded.

What about Adobe Acrobat Reader?

It can fill and sign, and it works. It is also a large app built around a subscription, and the signing tool is several taps deep inside a reader you may not want. If you already have it and you are happy, there is no reason to change. If you open it once a year to sign one form, a small app that opens straight onto the job is less friction.

Is an electronic signature legally valid?

For the overwhelming majority of everyday documents, yes. An electronic signature is recognised under the United States ESIGN Act and, in the European Union, as a simple electronic signature under eIDAS. Rental agreements, NDAs, school forms, invoices, consent forms and most commercial contracts are all routinely signed this way.

There is a second, different thing also called a "digital signature": a cryptographic signature backed by a certificate from a certificate authority, which makes Adobe Acrobat show a blue verification check. Some formal and government processes require exactly that. PDF Signer does not do it, and no free phone app does, because the certificate has to be issued to you personally. If that is what you have been asked for, you need dedicated software and a certificate. If you have simply been asked to "sign and send it back", what is described on this page is what you want.

A few things that trip people up

• Password-protected PDFs cannot be signed until the password is removed. Bank statements and payslips are often protected. Save an unprotected copy first, on a computer or in the app that produced the file.
• Scanned documents are fine. A PDF that is really a photo of a page signs exactly the same way, because the signature sits on top of the page.
• Check the result before you send it. Open the signed file in Drive or your usual reader and make sure the signature sits where you put it. It should, but thirty seconds of checking beats an awkward email.
• Photograph your signature in good light if you use the upload option, on white paper, with a dark pen. The app removes the paper and keeps the ink, and it can only do that well if the two are clearly different.

Do it now

PDF Signer is free, has no account, adds no watermark, and works offline. See what it does or read exactly what happens to your files.