The short answer: to sign a PDF on your phone, open OpenSign™ in your mobile browser, upload the PDF, tap to add a signature field, draw your signature with your finger, and download the signed file. It works on both iPhone and Android — no app to install — and produces a legally binding signature.
How to sign a PDF on iPhone
- Open Safari and go to app.opensignlabs.com, then sign in (free).
- Tap Sign Yourself and upload your PDF.
- Tap where you need to sign to place a signature field.
- Draw your signature with your finger, or type your name.
- Add date or text fields if needed, then finish.
- Download the signed PDF and certificate of completion.
How to sign a PDF on Android
The steps are identical on Android — open Chrome (or any browser), go to OpenSign, upload your PDF, place a signature field, draw with your finger, and download. Because OpenSign is fully browser-based, there's no separate app to download.
Tips for signing on mobile
- Turn your phone to landscape for a larger signing area.
- Zoom in to place fields precisely.
- Use a stylus for a cleaner drawn signature.
- Save your signature so you can reuse it next time.
Send a PDF to someone else from your phone
Use Request Signatures, add the recipient's email, place their fields and send — they'll sign on their own device. See the full how to sign a document online guide.
Ready to try it? Create a free OpenSign account and start signing documents in minutes — no credit card required. Prefer to run it yourself? OpenSign is 100% open source on GitHub.