Will Adobe Reader show the signature as valid?

Reader will confirm the document has not changed since signing. It shows the signer as trusted only if the certificate comes from a provider on its trust list, or if you add your certificate as trusted.

Does my certificate get uploaded?

No. The certificate file and password are only used inside this browser tab.

Are my files uploaded?

No. This tool runs entirely in your browser tab. Files are read from your disk into memory and the result is generated locally.

Is it free? Are there limits or watermarks?

Free and open source (MIT). There are no file-size caps, daily quotas, accounts or watermarks.

Does it work offline?

Yes, once the page (and any engine it needs) has loaded, it keeps working without a connection thanks to the service worker cache.

Home / PDF Tools / Digital Signature (Certificate)

Digital Signature (Certificate)

Sign a PDF with your .p12 or .pfx certificate, visibly or invisibly, without uploading it.

Free, no uploads, no sign-up. Runs 100% in your browser.

How Digital Signature (Certificate) works

node-forge opens your PKCS#12 certificate and builds a detached CMS signature (SHA-256) over the exact bytes of the PDF. The signature is appended as an incremental update, so earlier signatures stay valid. You can also create a self-signed test certificate with WebCrypto.

Input: PDF, P12, PFX. Output: PDF.

How to use Digital Signature (Certificate)

Drop your PDF onto the Digital Signature (Certificate) area, or click to choose it.
Wait a moment while page thumbnails render locally.
Choose the pages and options you need. Previews update as you go.
Press the main action button and download the finished PDF.

Tips

Encrypted PDFs must be unlocked first with Unlock PDF.
Large scanned PDFs are mostly images. Compress PDF shrinks them the most.
Your original file is never modified; you always download a new copy.

Digital Signature (Certificate) FAQ

Will Adobe Reader show the signature as valid?: Reader will confirm the document has not changed since signing. It shows the signer as trusted only if the certificate comes from a provider on its trust list, or if you add your certificate as trusted.
Does my certificate get uploaded?: No. The certificate file and password are only used inside this browser tab.
Are my files uploaded?: No. This tool runs entirely in your browser tab. Files are read from your disk into memory and the result is generated locally.
Is it free? Are there limits or watermarks?: Free and open source (MIT). There are no file-size caps, daily quotas, accounts or watermarks.
Does it work offline?: Yes, once the page (and any engine it needs) has loaded, it keeps working without a connection thanks to the service worker cache.

Related tools

Verify PDF Signatures: Check digital signatures: was the file changed, who signed it, certificate chain and timestamps.
Sign PDF: Draw, type or upload a signature and place it anywhere, plus dates and initials.
Protect PDF: Encrypt a PDF with a password and set print/copy permissions.
Merge PDF: Combine multiple PDFs into one ordered document with drag-and-drop sorting.