The simplest free way to sign a PDF on an Android phone is the Acrobat Reader app: open the PDF, tap Fill & Sign, tap Signature > Add signature, draw it with your finger, and tap the spot where it should go. If the document arrived as an e-signature request instead of an attachment, you don’t need any app at all, because the signing page opens in your browser.

What trips people up is that the Google Drive app, which most Android phones already have, can fill in a PDF form but doesn’t add signatures, at least not according to Google’s own help page. So here’s what works, with the steps taken from Adobe’s and Google’s documentation.

What’s the easiest way to sign a PDF on Android?

Install the free Acrobat Reader app and use its Fill & Sign tool, which works the same on any Android phone. Some phone makers ship their own PDF or note-taking apps with a signing option, but those differ from model to model, so I’m sticking to options that don’t depend on which phone you bought.

If you sign one thing a year and don’t want another app, skip ahead to the browser option below.

How do I sign a PDF in Acrobat Reader on Android?

Open the PDF, tap Fill & Sign in the bottom menu, then tap Signature > Add signature. Adobe’s steps for Acrobat on mobile:

  1. Open the PDF in Acrobat Reader and select Fill & Sign from the bottom menu.
  2. Select Signature > Add signature.
  3. Draw your signature, use an image, or capture one with the camera, then tap Done.
  4. Tap anywhere on the document to place your signature.
  5. To move it, hold and drag. To resize it, use the handles.
  6. Tap the checkmark to save.

Initials work the same way through Signature > Add initials. The same Fill & Sign menu has a Text box for typing your name or the date, plus checkmark, cross and radio-button marks for forms with tick boxes.

The capture option is the one I’d try first. Sign your name on a plain sheet of white paper with a dark pen and photograph it. It will look far more like your real signature than anything drawn with a fingertip on a 6-inch screen.

Can I fix my signature after saving?

No, so check before you tap the checkmark. Adobe says “Signatures and initials are permanent once saved. The PDF flattens on save and cannot be edited or unsigned afterward.” Flattening means your signature and anything you typed become part of the page itself, not separate items you can move later.

If there’s any chance you’ll need a do-over (wrong date, signed on the wrong line), save a copy of the unsigned PDF first. On a phone it’s easy to forget, and then you’re emailing the sender to ask for the original again.

What happened to the Adobe Fill & Sign app?

Adobe retired the standalone Fill & Sign app and replaced it with Acrobat Reader mobile, which Adobe says includes “all the familiar Fill & Sign features and more.” If you still have documents in the old app, Adobe’s note is worth reading before you delete it: “Your Fill & Sign app data and assets won’t be automatically migrated to the Acrobat Reader app.” You move them yourself, either by sharing each document to Acrobat Reader or by uploading them to Adobe cloud storage from the old app and signing in to Acrobat Reader with the same account. Adobe’s page walks through both.

Can I fill out and sign a PDF in Google Drive on Android?

You can fill out a PDF form in Google Drive on Android, but Google’s help page for it only covers typing into form fields, not signing. The steps:

  1. Open the Google Drive app.
  2. Tap the PDF you want to fill out.
  3. At the bottom right, tap Edit > Form filling. If you don’t see that option, Google says “you may not be able to fill out this PDF,” which usually means the form has no fillable fields.
  4. Enter your information.
  5. Tap Save at the top right, or use More > Save as to keep a copy.

Then add your signature with Acrobat Reader or a browser tool. It’s a two-app job, which is a bit clunky, but it works fine for a long form with lots of fields and one signature at the end. If you’re not sure whether a form is fillable at all, our guide on how to fill out a PDF form explains how to tell.

Can I sign a PDF on Android without installing an app?

Yes. A browser-based signing tool runs in Chrome or whatever browser your phone uses. We built a free Sign a PDF tool for this: pick the PDF from your phone, type or draw a signature, tap where it goes, add the date if you need it, and download the signed copy. It never uploads your file (everything happens inside the browser), there’s no account, and it handles files up to 25 MB.

The honest caveat is the same one that applies to Acrobat’s Fill & Sign: the result is a picture of your signature on the page. It doesn’t seal the file or record when you signed. For a school form or a delivery note, that doesn’t matter. For a contract with real money attached, see the next section.

What if someone sent me the document to e-sign?

Then you don’t need to download the PDF at all. Open the email, tap the link, and follow the prompts on the signing page. Each e-signature service looks a little different, but the steps are similar. Google’s eSignature feature, as an example, describes it like this for signers:

  1. Open the email notification and click the embedded link.
  2. Tap any colored fields, which are the ones assigned to you, and fill in any text fields such as a job title.
  3. Create your signature by typing your name or drawing it. Google says you can draw with “your mouse, trackpad, or touchscreen.”
  4. Tap Adopt and sign, then Mark Complete once every required field is done.
  5. Review and accept the terms, and tap Agree & Continue.

When everyone has signed, Google says each signer gets a link to the final copy by email, and a personal copy lands in their My Drive. The finished PDF ends with an audit trail page logging when the request was sent, signed and completed. That record is the real difference from signing a PDF yourself in an app. If you’re curious what goes into one, we explain it in what is an e-signature audit trail.

Which option should I use?

Use the email link when you got a signing request, Acrobat Reader when someone emailed you a PDF and you sign things on your phone often, and a browser tool when you just need to sign one file and move on.

Here’s a hypothetical. Priya walks dogs for a living and a new client emails her a two-page service agreement as a PDF. She’s at the park between walks, phone only. She opens it in Acrobat Reader, signs with a captured photo of her signature, saves, and replies with the signed file in under five minutes. That’s fine for her side. But if she wanted her own clients to sign her agreement from their phones, and have a record of when they did, sending it through an e-signature service would save her chasing attachments around. Our guide on how to sign a PDF online covers the computer side of the same choices. That’s the job SignWren is built for, and you can start free.