What is the difference between a digital signature and an electronic signature?

An electronic signature (e-signature) is any mark indicating intent to sign, such as typing your name or drawing a signature image. A digital signature uses cryptographic certificates to create a mathematically verifiable proof that the signer is who they claim to be and that the document has not been altered since signing. Digital signatures provide non-repudiation and tamper detection that simple e-signatures cannot.

What certificate format do I need?

You need a PFX (also called P12 or PKCS#12) file containing your signing certificate and private key. These are issued by certificate authorities like DigiCert, GlobalSign, or your organization's internal CA. Self-signed certificates can also be used for internal workflows, though they won't be trusted by external parties without prior key exchange.

Can recipients verify my digital signature?

Yes. Any PDF viewer that supports digital signatures (Adobe Acrobat, Foxit Reader, most modern viewers) can verify the signature. The viewer checks that the certificate is valid, the document has not been modified after signing, and the signing time is within the certificate's validity period. If you used a certificate from a trusted CA, the signature will show as valid automatically.

Is my private key safe during the signing process?

Yes. The entire signing operation happens locally in your browser using WebAssembly. Your PFX file and private key are loaded into browser memory, used to compute the signature, and then discarded when you close the page. No keys or documents are transmitted to any server.

Digital Sign PDF

Add a cryptographic digital signature to your PDF documents directly in the browser. Unlike visual signatures (drawing your name), digital signatures use public-key cryptography to create a tamper-evident seal that proves the document has not been modified after signing. This is essential for contracts, regulatory submissions, certified documents, and any workflow requiring non-repudiation. Recipients can verify the signature to confirm the signer's identity and document integrity. Our tool processes everything locally via WebAssembly, so your private keys and sensitive documents never leave your device.

Requires certificate server

Powerful Digital Sign PDF Features

Cryptographic Security

PKCS#7 digital signatures provide mathematical proof of signer identity and document integrity.

Private Key Protection

Your certificate and private key never leave your device. All cryptographic operations run locally.

Verifiable Signatures

Recipients can validate signatures in Adobe Acrobat and other viewers to confirm authenticity.

How To Digital Sign PDF Online for Free

Upload PDF and Certificate

Drop your PDF and PFX certificate file into the tool. Enter your certificate password. Everything stays on your device.

Configure Signature

Choose visible or invisible signature, set position and size, and optionally add a reason and location for the signature.

Sign and Download

Apply the cryptographic signature and download your signed PDF. Recipients can verify it in any compatible PDF viewer.

Everything You Need in a Digital Sign PDF

PKCS#7 Standard

Uses industry-standard CMS signatures compatible with all major PDF viewers and validation tools.

PFX Certificate Support

Load your PFX/P12 certificate file directly. Supports certificates from any issuing authority.

Visible or Invisible

Add a visible signature stamp on the page or an invisible signature that only appears in the signature panel.

Timestamp Support

Include a signing timestamp to prove exactly when the document was signed for legal compliance.

Tamper Detection

Any modification after signing invalidates the signature, immediately alerting recipients to changes.

Local Crypto Engine

WebAssembly performs all cryptographic operations on your device. No keys or documents are transmitted anywhere.

Frequently Asked Questions

Document Work Made Easy

Process your PDFs with our collection of free, privacy-first tools. No uploads to servers, no registration required. Everything runs directly in your browser.