How to sign a PDF
Checked against our tools on 17 October 2026
For most forms, letters and agreements someone emails you, open Sign PDF, draw your signature or upload a picture of it, click where it goes and download. If the recipient asks for a digital signature, or you need to prove the file hasn't changed since you signed, use Sign with a certificate and your .p12 or .pfx certificate file. Both run in your browser, so the document never leaves your device.
Go straight to the tool: Sign PDF, Sign with a certificate
Two different things are both called signing
A drawn signature is a picture of your handwriting placed on the page, like signing a printout and scanning it. It shows that you agreed, which is all most landlords, schools and HR teams ask for. It doesn't stop anyone editing the PDF afterwards, and it doesn't prove by itself who placed it.
A digital signature is cryptographic data inside the PDF, made with a certificate that belongs to you. A PDF reader can check it: if anything in the file changes after signing, the reader says the signature is invalid. If your certificate comes from an authority the reader trusts, it also shows your verified name. You need a certificate file to make one.
| Drawn signature | Digital signature | |
|---|---|---|
| What you need | Your mouse, finger or a photo of your signature | A .p12 or .pfx certificate and its password |
| Shows on the page | Yes | No; readers show it in a signature panel |
| Detects later edits | No | Yes |
| Proves who signed | No | Only with a certificate from a trusted authority |
| Typical use | Forms, leases, permission slips, offer letters | Contracts, tenders, government and finance paperwork that asks for it |
Sign with a drawn signature
- Open Sign PDF and add the document.
- Draw your signature in the box with a mouse, trackpad or finger, or upload a photo of it. A PNG with a transparent background looks most natural.
- Go to the right page and click where the signature should go, then download the signed copy.
Sign with a certificate
- Finish every other change first: fill in the form, add a drawn signature if you want one on the page, remove pages. Any edit after this step breaks the signature.
- Open Sign with a certificate and add the finished PDF.
- Choose your .p12 or .pfx file and enter its password.
- Sign and download. Open the result in Adobe Acrobat Reader and check the signature panel to see what the recipient will see.
Where certificates come from
Some employers, universities and governments issue them; in Europe, a qualified certificate under eIDAS is the strongest kind. Commercial certificate authorities sell document-signing certificates. You can also make a self-signed certificate for free. It still proves the file hasn't changed since you signed, but readers will say the signer's identity can't be verified, because no authority vouched for it.
Our tool supports RSA certificates. Elliptic-curve certificates aren't supported yet.
What breaks a signature
Adding a drawn signature, filling a field, merging, compressing or rotating pages after a digital signature all rewrite the file, and the digital signature then shows as invalid. That's the signature doing its job. Do everything else first and sign last. If several people need to sign digitally, each should sign in turn without changing anything else.
For the same reason, Sign with a certificate leaves an already-signed PDF alone rather than rewriting it.
Is an electronic signature legally valid?
In many countries, yes, for most everyday documents. The US ESIGN Act of 2000, the EU's eIDAS regulation and Australia's Electronic Transactions Act 1999 all accept electronic signatures in general. All of them have exceptions, though, and wills and some property documents often still need ink. When it matters, ask whoever wants the signature what they accept. That's not legal advice, just the question worth asking.
Your document and certificate stay on your device
Both tools run in your browser. The PDF, your signature image, your certificate and its password are never uploaded, so there's no copy of them on our servers to leak. Online signing services that keep an audit trail need to store your document; this doesn't.