How to Sign a PDF on Android

Before you tap anything, it helps to know there are two different things people call a signature, and they are not the same.

The first is an electronic signature: a picture of your handwriting placed on the page, or a typed name styled to look signed. This is what almost every lease, consent form, and ordinary business agreement asks for. In the United States it is legally binding under the ESIGN Act and UETA, and it is what this guide mostly covers.

The second is a cryptographic digital signature. That one uses a certificate issued by a certificate authority and public-key encryption to bind your identity to the file and prove it has not been altered since you signed. It is a specific, narrower thing. A drawn signature is fine for daily documents, but it is not a cryptographic digital signature, and a few institutions (some courts, some government filings, some regulated finance and healthcare paperwork) will only accept the certificate kind. If the sender mentions a "qualified" or "certificate-based" signature, skip ahead to the section on that. For everything else, read on.

Xodo (full name "PDF Reader & Editor: Xodo" on Google Play) is a free PDF app that handles signing well and does not nag you much. It was last updated in June 2026, so the steps below match the current version.

After you install it and open the PDF:

1. Tap the document to bring up the toolbar, then open the Fill and Sign tool. Use this to tick checkboxes and type into any blank fields first, before you sign.
2. Choose the Signature option. The first time, Xodo asks you to create one. You can draw with your finger, type your name and pick a handwriting style, or import a photo of your real signature.
3. If you want to use your actual ink signature, sign a blank white sheet, photograph it in good light, and import that image. It reads far cleaner than a finger scrawl.
4. Tap where the signature goes, then drag the corner handles to size it and move it to sit on the signature line.
5. Add the date the same way using the text tool if the form asks for one.

Xodo also has a built-in scanner, which is useful if part of your task is turning a paper page into a PDF first. If you are weighing it against other options, it appears on our roundup of the best PDF editor apps for Android, and it sits in the wider ultimate list of free Android PDF editors if you want to compare the free tiers side by side.

Adobe Acrobat Reader is the other dependable free choice, and a lot of senders expect it because it is the app that made the format. The signing tool you want is called Fill and Sign, and it works without a paid subscription and without an internet connection.

1. Open the PDF, then tap the Fill and Sign tool from the bottom menu.
2. To add your signature, tap Signature, then Add signature. You can draw it, type it, snap a photo with the camera, or import an existing image.
3. Tap Done, then tap anywhere on the document to drop the signature in place.
4. To reposition it, press and hold, then drag. To resize, pull the handles. To remove it, tap it and choose Delete.

One thing to know about Acrobat: signatures and initials become permanent once you save, and the file flattens on save, so it cannot be unsigned afterward. That is usually what you want, but it means you should fill in every field before that final save. Acrobat is also covered on our list of the best PDF reader apps for Android if reading and annotating are a bigger part of your routine than signing.

A signature on a blank form is not much use. Most contracts and applications have name, date, address, and checkbox fields that need filling too. Both apps handle this through the same Fill and Sign mode you used for the signature.

If the PDF was built as a real form, the fields are interactive and you just tap into them. If it is a flat scan with printed lines, you place text boxes manually where the answers go. Type the field, drag it onto the line, and shrink the font so it sits cleanly. Do this for every field before you sign, because in Acrobat the save step locks everything at once. Tidy form work like this is part of a calmer phone productivity setup, and it saves you re-sending a half-filled document.

Take thirty seconds to proofread once everything is placed. A misspelled name on a signed contract is annoying to fix after the file is flattened.

Here is the step people skip, and it matters. When you place a signature as an annotation, it can technically be dragged, resized, or deleted by anyone who opens the file in an editor. Flattening fixes that. Flattening merges every annotation, form field, and signature into the page itself, like ink soaking into paper. The content stays visible but is no longer editable or movable.

In Acrobat, this happens automatically: the file flattens when you save, so you do not need a separate step. In Xodo, do it yourself. Tap Save a Copy, then choose Flattened Copy from the menu. Send that flattened copy, not the original working file.

One caution: flattening is permanent. You cannot un-flatten a PDF to get the editable fields back. So keep your unflattened version if you might need to change something, and only flatten the copy you are about to send.

Once the file is signed and flattened, share it straight from the app. Use the share icon and send through email or your messaging app, or save it to Google Drive and share a link if the file is large.

Two small habits help. Send a PDF, never a screenshot of the screen, because the recipient often needs to file the actual document. And name the file something clear like "lease-signed-yourname.pdf" so the person on the other end does not have to guess.

Most of the time the routes above are all you need. But be honest with yourself about the document. A drawn or photographed e-signature is valid for everyday agreements, yet it carries less weight in a dispute than a certificate-based digital signature, which provides cryptographic proof of who signed and that nothing changed afterward.

Some institutions require that stronger kind. Certain court filings, government submissions, and regulated finance or healthcare paperwork ask for a digital signature backed by a certificate from a certificate authority, sometimes a "qualified" signature in Europe. You cannot produce that with the free Fill and Sign tools; it needs a digital ID issued to you, set up through a service such as Adobe Acrobat Sign or a national e-ID scheme. If the sender uses the words "certificate," "digital ID," or "qualified electronic signature," ask them which provider they expect before you sign anything, so your signature is actually accepted.