Sign a PDF with Your Digital Certificate (.p12 / .pfx)
Add a real cryptographic signature with your own certificate. The PDF and the certificate never leave your device.
Your PDF and your certificate never leave this device. The signature is calculated in your browser.
1. The PDF to sign
Drop the PDF here
or
Stays on your device - nothing is uploaded
2. Your digital certificate
3. Signature details
How to use Sign PDF with Digital Certificate
- 1Choose the PDFIt is read in your browser. Nothing is uploaded at any point.
- 2Open your certificatePick your .p12 or .pfx file and type its password. You will see the holder, issuer and validity dates.
- 3Add the detailsOptionally a reason and place, and a visible signature box on the first or last page.
- 4Sign and downloadThe signed PDF downloads straight away. Adobe Acrobat Reader shows the signature in its signature panel.
Your files are processed over an encrypted connection and deleted automatically within one hour. Nothing is shared with anyone.
Frequently asked questions
What is the difference from drawing a signature?
A drawn signature is a picture. A certificate signature is cryptographic: it proves which certificate signed the file and that nothing has changed since. Edit one byte afterwards and readers report the signature as invalid.
Is my certificate uploaded?
No. The certificate file, its password and the PDF are only read inside your browser, and the signature is calculated there. That is the point of this tool: a certificate contains your private key, which should never be sent to a website.
Which certificates work?
Any personal certificate exported as .p12 or .pfx with its private key, such as an FNMT certificate in Spain, an ICP-Brasil A1 certificate in Brazil or a certificate from your company. Certificates stored on a smart card or USB token cannot be used from a web page.
Will it show as valid?
The signature is a standard PKCS#7 signature with SHA-256. Readers mark it valid when they trust the authority that issued your certificate; certificates from national authorities are usually trusted, self-made ones are not. There is no timestamp from a time-stamping service.
Is this tool free?
Yes. Every tool on WorkSathi is free to use with no sign up, no watermark on your result and no daily limit.
What happens to my files?
Files are uploaded over an encrypted connection, processed, and then deleted automatically within one hour. We never open, share or sell your documents.
Does it work on a phone?
Yes. The tools work in any modern browser on Windows, Mac, Android and iOS - there is nothing to install.
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