Sign PDF
Sign PDF documents online for free — draw or type your signature and place it on any page.
Drop a PDF to sign
Your file stays on your device — nothing is uploaded
Up to 25 MB per file
Why NinjaPDF beats iLovePDF, Sejda & Smallpdf for signing
Most “free” PDF signers upload your document to their servers and cap how many files you can sign per day. NinjaPDF signs PDFs directly in your browser — your file never leaves your device.
| Feature | NinjaPDF | iLovePDF | Sejda | Smallpdf |
|---|---|---|---|---|
| 100% in-browser (no upload) | Yes | No — uploads to server | No — uploads to server | No — uploads to server |
| Free signatures per day | Unlimited | Limited on free plan | 3 tasks / hour | 2 documents / day |
| Sign-up required | No | Required beyond limits | Required beyond limits | Required beyond limits |
| Watermark on output | Never | No | No | No |
| Works offline after page load | Yes | No | No | No |
| File size limit | Only your device's memory | Capped on free plan | 200 pages / 50 MB | Capped on free plan |
Private by design
Your PDF is opened, signed and saved entirely in your browser. Nothing is uploaded, stored or processed on our servers — unlike iLovePDF, Sejda and Smallpdf.
Truly free, no limits
Sign as many PDFs as you want with no daily caps, no account, and no watermark — the kind of free that competitors gate behind paid plans.
Fast & offline-ready
No server round-trip means signing is instant, even on large files, and keeps working if your connection drops mid-session.
About Sign PDF
Sign PDF lets you add a signature to any PDF document online, free, with no sign-up. NinjaPDF's PDF signer works entirely in your browser — draw your signature with a mouse or trackpad, type it in a handwritten font, place it anywhere on any page, then download the signed PDF. Your document never leaves your device, which makes it ideal for contracts, NDAs, offer letters and any sensitive paperwork where uploading to a third-party server isn't an option.
How to use Sign PDF
- 1
Upload the PDF you want to sign by dragging it in or clicking ‘Choose file’. Your file stays on your device.
- 2
Draw your signature on the pad with a mouse or trackpad, or type your name and pick a handwriting style.
- 3
Choose the page, then drag the signature to the exact spot where it should appear and resize it if needed.
- 4
Click ‘Apply & download’ to save your signed PDF — ready to email, print or archive in seconds.
Why use NinjaPDF
- Free PDF signature with no watermark and no account
- Draw or type your signature in any color
- Place signatures on any page at any position
- 100% private — files never leave your browser
- Works on Windows, macOS, Linux, iOS and Android
- Output is a standard signed PDF accepted everywhere
Frequently asked questions
How do I add a signature to a PDF for free?+
Open NinjaPDF's Sign PDF tool, upload your document, draw or type your signature, drag it onto the page where it belongs and click Apply & download. There's no sign-up, no watermark and no daily limit.
Is it really free to sign PDF online?+
Yes. NinjaPDF's PDF signer is 100% free. You can sign as many PDFs as you want with no account, no credit card and no watermark on the output.
Are my documents uploaded to a server when I sign?+
No. The entire PDF signature process runs locally in your browser using WebAssembly. Your contract, NDA or agreement never leaves your computer.
Can I sign a PDF on my phone?+
Yes. The signature pad works with finger touch on iOS and Android, so you can sign PDFs on the go just as easily as on a desktop.
Is a drawn signature on a PDF legally binding?+
In most jurisdictions, including the US (E-SIGN Act) and EU (eIDAS), a drawn or typed signature on a PDF is legally binding for routine business documents. For contracts requiring qualified e-signatures, check your local regulations.
Can I add multiple signatures or initials to one PDF?+
Yes. After placing a signature, you can add more on the same page or jump to other pages and drop additional signatures or initials wherever needed.
Does signing change the rest of the PDF content?+
No. NinjaPDF only stamps the signature image onto the page you choose. The original text, formatting and other pages stay untouched.