Digital Signature
Add X.509 digital signatures to PDF documents. Sign PDFs with PFX, P12, or PEM certificates for legal validity.
Upload PDF to Sign
About This Tool
Digital Sign PDF applies cryptographic digital signatures, not just images of a signature, using local certificates in P12 or PFX format or certificates from trusted authorities. The resulting signature verifies the signer's identity and detects any later modification to the document. This is signing in the legal and technical sense, with the audit trail built into the file.
Engineers sign deliverables that clients verify for authenticity before acceptance. Compliance teams sign documents where a black-ink claim must be provable through the certificate chain. Anyone whose documents are audited needs a signature that is mathematically examinable, not merely branded onto a page. Signed output remains valid in standard readers, and the embedded cryptographic data stays verifiable long after the file moves between systems.
Signing is performed locally in your browser, so your certificate and the document never leave the machine. After signing, run a validation to confirm the result verifies cleanly in other readers. Free, no account, and real signatures with real verification, not ink.
Practical guidance before you use Digital Signature
Best for real document workflows
Use Digital Signature when you need a quick browser-based result without creating an account or sending routine documents through an unnecessary upload workflow. Legal Documents is a common example: Sign contracts, agreements, and legal documents with legally binding digital signatures.
Privacy and file handling
EasyPDFNex prioritizes local processing in your browser. That means supported PDF operations run on your device, not in a public cloud queue. For sensitive files, review the output before sharing it, close the browser tab after downloading, and avoid processing documents you are not authorized to edit.
Quality checks after processing
After you sign and download, open the result and check page order, text readability, signatures, links, and form fields. If the source file is scanned, encrypted, very large, or damaged, try a related workflow such as validate signature, encrypt pdf, sign pdf before repeating the task.
Start with a clean source file whenever possible. For Digital Signature, the first step is usually "Upload PDF": Upload the PDF document you want to digitally sign. This simple preparation step prevents most failed exports, missing pages, and formatting surprises.
Editorial review note
This guidance is maintained by the EasyPDFNex editorial team and reviewed for practical PDF workflow accuracy. Tool pages are written to explain when a feature is useful, what to check before download, and where browser-based processing has limits.
How to Use
Upload PDF
Upload the PDF document you want to digitally sign.
Load Certificate
Upload your X.509 certificate file (.pfx, .p12, or .pem) and enter the password.
Configure Signature
Optionally add reason, location, and visible signature with custom text or image.
Sign and Download
Click Sign PDF to apply the digital signature and download the signed document.
Use Cases
Legal Documents
Sign contracts, agreements, and legal documents with legally binding digital signatures.
Business Approvals
Digitally sign invoices, purchase orders, and approval documents for audit trails.
Document Integrity
Ensure documents have not been tampered with after signing.
Frequently Asked Questions
What certificate formats are supported?
PFX (.pfx), PKCS#12 (.p12), and PEM (.pem) certificate formats are supported.
Is the signature legally valid?
Yes, X.509 digital signatures are legally recognized in most jurisdictions when using a valid certificate.
Can I add a visible signature?
Yes, you can add a visible signature with custom text, image, position, and styling.