Need to sign a PDF on your Android phone but don't want to print, scan, or pay for a subscription? You're in luck. There are several genuinely free ways to add a legally valid signature to a PDF directly on Android — no printer, no desktop, and no watermarks required. If you're on an iPhone instead, see our guide to signing a PDF on iPhone. This guide walks through the three best options with clear steps so you can choose what works for your situation.
Method 1 — PrimeDocu (Best Overall)
PrimeDocu is a web-based document management app that works directly in Chrome on Android. Because it runs in the browser, there's nothing to install — just open the site and you're ready to go. Signed documents are stored in an AES-256-GCM encrypted vault so only you can access them, and the free plan covers unlimited PDF signing with no watermarks.
- Open Chrome on your Android device and navigate to www.primedocu.com/home. Create a free account — no credit card needed.
- Tap the upload button and choose the PDF you want to sign from your Downloads folder, Google Drive, or anywhere else on your device.
- Tap the Signature tool in the toolbar. You have three options: draw your signature with your finger, type your name in a cursive font, or upload a photo of your ink signature.
- Drag the signature block to the correct position on the document. Resize it if needed by pinching.
- Tap Save. The signed PDF is saved to your encrypted vault and can be downloaded or shared at any time.
The whole process takes under two minutes and the result is a standard PDF with your signature embedded — no proprietary format, no lock-in. Because the vault is zero-knowledge encrypted, not even PrimeDocu can read your documents.
Method 2 — Google Drive
If the PDF is already in Google Drive, you can add a basic markup annotation using Google's built-in tools, though this approach is more limited than a dedicated signing tool.
- Open the Google Drive app and tap the PDF you want to sign.
- Tap the pencil/edit icon to open the document in Google Docs or the PDF viewer.
- Use the Draw annotation tool to draw a signature shape with your finger at the desired location.
- Download the annotated PDF.
The limitation here is that Google Drive's annotation is a freehand drawing, not a proper signature field. It works in a pinch but the result can look rough, and there's no option to type or upload a signature image. For anything more formal — a lease, a contract, an NDA — Method 1 produces a more professional result.
Method 3 — Adobe Fill & Sign (Android App)
Adobe offers a dedicated Android app called Adobe Fill & Sign that is free for basic signing. It handles both form filling and signature placement well, which makes it a good option if you regularly deal with PDF forms that have fillable fields.
- Download Adobe Fill & Sign from the Google Play Store.
- Open the app, tap Select a file, and choose your PDF.
- Tap the signature pen icon in the toolbar and draw your signature or initials. Adobe stores this for future use.
- Tap anywhere on the document to place the signature, then drag it into position.
- Save and share the signed PDF from within the app.
The free tier of Adobe Fill & Sign is functional, but Adobe's ecosystem tends to push users toward paid Creative Cloud plans, and documents are stored in Adobe Document Cloud rather than an end-to-end encrypted vault. If document privacy matters to you, this is worth considering.
Comparison: Android PDF Signing Methods
| Feature | PrimeDocu | Google Drive | Adobe Fill & Sign |
|---|---|---|---|
| Cost | Free (unlimited signing) | Free | Free (basic) |
| App download required | No — works in Chrome | No (if Drive installed) | Yes |
| Signature styles | Draw, type, upload image | Draw only | Draw, type |
| Watermark on free plan | None | None | None |
| Encrypted storage | Yes — AES-256-GCM | No (Google holds keys) | No (Adobe cloud) |
| Legally binding | Yes | Yes (annotation) | Yes |
| Best for | Most use cases | Quick annotation | Form-heavy PDFs |
Which Method Should You Use?
For the majority of Android users, PrimeDocu is the best all-round choice. It requires no app installation, produces a clean professional signature, stores your document securely, and is completely free with no watermarks. Google Drive works if you need a very quick annotation and already have the PDF there. Adobe Fill & Sign is worth considering if you spend a lot of time filling out PDF forms specifically.
Whichever method you choose, remember that an electronic signature drawn on your phone is legally valid for most contracts, NDAs, offer letters, consent forms, and rental agreements under both US and EU law. The key is that you intend to sign — the method of capture is secondary.
Frequently asked questions
Can I sign a PDF on Android for free?
Yes. PrimeDocu lets you sign unlimited PDFs for free with no watermarks and no credit card required. Open www.primedocu.com/home in Chrome on your Android device, upload your PDF, and sign in under two minutes.
Is a signature drawn on Android legally valid?
Yes. Under the US ESIGN Act (2000) and the EU eIDAS Regulation, an electronic signature — including one drawn with your finger on a touchscreen — is legally equivalent to a handwritten signature for the vast majority of contracts and everyday documents.
Does a signed PDF look the same as a handwritten signature?
It can look very natural. When you draw your signature with your finger using PrimeDocu, the resulting mark on the PDF resembles a genuine handwritten signature. You can also upload a photo of your real ink signature for an identical appearance.
Do I need to print a PDF to sign it on Android?
No. All three methods described in this article let you sign a PDF entirely digitally on your Android phone, without printing, scanning, or a desktop computer.