How to sign a PDF on Android

Why Android has no built-in signing tool

Apple added PDF annotation and Markup to iOS early on, integrating it into the Files app and the Mail app so signing a PDF is a few taps away from wherever you received it. Google has not built an equivalent into stock Android. Chrome on Android added a native PDF viewer in 2024 that includes basic markup tools — a pen and highlighter — but those produce annotation overlays, not proper electronic signatures, and the resulting file is not a flattened, signed PDF suitable for returning to a counterparty.

The practical result is that most Android users either install a third-party app or use a cloud service. Both approaches work, but both have trade-offs. The browser approach eliminates those trade-offs: no install, no account, no server upload.

Why skip a Play Store app?

Most free PDF signing apps on Android are ad-supported, request broad storage and network permissions, and upload your document to their servers to process it. For a one-minute signing task, that is a disproportionate set of trade-offs.

Signing in the browser avoids all of them: nothing is installed on your device, no permissions beyond picking a file are requested, and the document is processed locally using WebAssembly rather than being transmitted to a server. The result is a proper, flattened signed PDF — not an annotation overlay.

Signing a PDF from Gmail or Google Drive

If the PDF is a Gmail attachment, tap and hold the attachment, choose Save to Drive or Download, and then upload it in the DocSignHub signer. Alternatively, tap the attachment to open it in the Gmail viewer, then use the share button to save it to Files or Download — then open the signer and pick it from there.

From Google Drive, open the file preview, tap the three-dot menu, and choose Download. The file lands in your Downloads folder, where you can pick it in the signer. After signing and downloading the completed PDF, share it back via the Android share sheet — attach it to an email reply, upload to Drive, or send it via any sharing app.

Works on any Android phone or tablet

Because it runs in the browser, the same signing flow works on any Android device — Samsung, Pixel, OnePlus, Xiaomi, and every other manufacturer. There is nothing device-specific to set up, no launcher requirement, and no dependency on a Samsung app or a Pixel feature.

On Android tablets — particularly Samsung Galaxy Tab devices — a stylus makes drawing a signature especially clean and precise. The larger screen also helps with placement accuracy on dense form documents. The same browser signer works on all of them without any modification.

Drawing a good signature on a small phone screen

Signing with a fingertip on a small screen can produce cramped or shaky strokes. Draw larger than you think you need — fill the signature pad generously — and then resize the signature down when placing it on the page. Scaling down hides small irregularities and produces a cleaner result.

If you find drawing on a phone screen too difficult, type your name in a handwriting font instead. A typed signature is a valid electronic signature under the ESIGN Act and eIDAS, and it looks consistent every time. If your phone supports Samsung DeX or a USB-C stylus, those can also improve drawing precision.

Accessing PDFs stored on your Android device

Android's file picker in Chrome shows all storage providers your device recognizes, including local device storage, Google Drive, and Dropbox if installed. You can pick a PDF directly from any of those locations in the upload dialog without downloading it to local storage first.

PDFs received via WhatsApp are saved in a WhatsApp-specific folder in internal storage. Open Files by Google, navigate to Internal Storage > Android > media > com.whatsapp > WhatsApp > Media > WhatsApp Documents, and you will find them there. Pick the file from that location in the signer.

Privacy: your document stays on your phone

The PDF never leaves your Android device. WebAssembly processes the document entirely in your browser's memory, so there is no server transmission and no copy created anywhere outside your phone. This is particularly important when signing sensitive personal documents — a bank form, a healthcare consent, a lease — on a mobile connection where you cannot verify the network.

Once you download the signed file, it is stored in your Downloads folder on the device. From there, send it only to the party that requested it.

Troubleshooting on Android

If the file picker does not show a PDF you know is on the device, try opening the Files by Google app first to make sure the file is indexed, then retry the upload dialog. If you are picking from Google Drive and the file is not visible, ensure you are connected to the internet (Drive requires a connection to show cloud files in the picker even if they are cached).

• >PDF not appearing in picker: open Files by Google, navigate to the file, then retry.
• >Cannot find WhatsApp PDF: navigate to Internal Storage > Android > media > com.whatsapp > WhatsApp > Media > WhatsApp Documents.
• >Signature looks shaky: draw larger in the signature pad and scale down on the page.
• >Download not saving: check that Chrome has storage permission in Android Settings > Apps > Chrome > Permissions.