AirPDF
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True PDF Digital Signature & PKCS#7 Certificate Stamper

Sign PDF documents with tamper-evident cryptographic digital signatures (PKCS#7 / PAdES) directly in your browser. Use your own .p12/.pfx certificate or generate an in-browser self-signed X.509 certificate with optional certified visual stamps. 100% private, zero server uploads.

Select PDF to Cryptographically Sign

Drag & drop contracts, agreements, or invoices here, or click to browse.

Choose PDF Document
100% In-Browser • PKCS#7 / PAdES Detached • Tamper-Evident • Adobe Acrobat Compatible

How to use True PDF Digital Signature & PKCS#7 Certificate Stamper

1

Upload PDF Document

Drag and drop the contract, legal agreement, invoice, or certificate you need to cryptographically sign.

2

Choose or Generate X.509 Certificate

Upload an existing corporate .p12 or .pfx certificate, or generate an instant in-browser self-signed certificate with your name and organization.

3

Configure Signer Details & Visual Stamp

Enter your signer name, signing reason, location, and customize optional on-page certified visual stamp badge.

4

Sign & Download Cryptographic PDF

Click Sign Cryptographically to compute the SHA-256 digest, embed the PKCS#7 detached signature dictionary, and download your tamper-evident PDF.

Authentic Cryptographic PDF Digital Signatures Without Monthly Subscriptions

Commercial signing platforms like DocuSign ($120–$480/yr) and Adobe Acrobat Pro ($239/yr) charge expensive recurring subscriptions or per-signature fees. Worse, they require you to upload confidential legal agreements, financial settlements, employment contracts, and NDA documents to third-party cloud servers where they are stored outside your control.

AirPDF’s True PDF Digital Signature & PKCS#7 Certificate Stamper brings enterprise-grade cryptographic signing into your web browser—100% free, 100% private, and completely offline.

Cryptographic Standards & Integrity

  1. PKCS#7 / CMS Detached Signatures (adbe.pkcs7.detached): In strict compliance with ISO 32000-1 and PAdES specifications, AirPDF calculates the SHA-256 message digest over the complete PDF byte stream (excluding only the signature contents container) and seals it with your RSA private key.

  2. Dual Certificate Options:

    • Upload Existing PKCS#12 (.p12 / .pfx): Easily sign with corporate PKI certificates, legal authority credentials, or identity certs.
    • Instant In-Browser X.509 Generator: Generate a 2048-bit RSA self-signed certificate on demand with your Name, Organization, Country, and custom validity period.

  3. Tamper-Evident Document Protection: Unlike simple image stamps that can be removed with any basic PDF editor, a cryptographic digital signature binds the exact content of every page. Any post-signing alteration, unauthorized page deletion, or text manipulation permanently breaks the cryptographic hash, warning any recipient who opens the file in Adobe Acrobat or Foxit Reader.

  4. Certified Visual Appearance Stamp: Includes an optional professional visual certification badge displaying your name, exact UTC signing timestamp, signing reason, and SHA-256 document fingerprint, ensuring your signature is instantly visible both on paper printouts and on screen.

Frequently Asked Questions

What is the difference between an Electronic Signature and a Cryptographic Digital Signature? ▼

An electronic signature is merely an image of your signature stamped onto a page, which provides no tamper protection and can easily be altered or copied. A Cryptographic Digital Signature (PKCS#7 / PAdES) hashes the entire binary content of the PDF and encrypts it with your private key. If even a single comma or byte is modified after signing, Adobe Acrobat and PDF validators immediately flag the signature as invalid and tampered.

Can I use my existing .p12 or .pfx digital certificate? ▼

Yes. If your company, government agency, or certificate authority (such as DigiCert, Sectigo, or GlobalSign) provided you with a .p12 or .pfx certificate bundle, simply upload it and provide your password. AirPDF parses the private key and certificate chain entirely in browser memory.

What if I do not have a .p12 certificate file? ▼

AirPDF includes a built-in cryptographic certificate generator. You can generate a self-signed X.509 v3 certificate with 2048-bit RSA encryption right in your browser. This is ideal for internal approvals, author verification, and establishing a cryptographic proof of document integrity.

Will my digital signature be recognized by Adobe Acrobat Reader? ▼

Yes. AirPDF implements the official ISO 32000-1 digital signature standard with /Filter /Adobe.PPKLite and /SubFilter /adbe.pkcs7.detached. When opened in Adobe Acrobat Reader, the Signature Panel will display the signature details, timestamp, certificate subject, and confirm that the document has not been modified since signing.

Is my private key or document uploaded to a server? ▼

Never. All RSA key generation, certificate parsing, SHA-256 hashing, and PKCS#7 signature generation execute exclusively in your browser RAM via WebAssembly and JavaScript. Your private keys, passwords, and sensitive contracts never touch any remote server.

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