Does your Google Doc™ still match your printed copy?
With Document Sealer, you'll always know for certain.

Document Sealer embeds a cryptographic seal (QR code + short verification code) directly into your Google Docs™ footer or Google Sheets™ tab. 

Because physical copies could be manipulated or reprinted, Document Sealer anchors trust where it matters most: it verifies the LIVE CLOUD DIGITAL COPY. Anyone with access to the Google Document or holding their printed copy can use the QR code or verification code to verify whether the current cloud version still matches the authentic sealed version, ensuring no silent edits were made.


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🔐 How It Works
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1. Seal: Document Sealer computes a SHA-256 cryptographic fingerprint of your document, signs it with HMAC-SHA256, and generates a tamper-evident seal — running 100% inside your Google account with zero external servers.

2. Print & Embed: The seal appears seamlessly right where you need it:
• Google Docs™: Embedded directly in the document footer.
• Google Sheets™: Inserted as a dedicated, clean "Document Sealer Seal" tab.

3. Verify: Verification takes seconds:
• In-App: Open the sidebar → Verify tab → click "Verify Current Document".
• From Printed Copy: Scan the printed QR code or type the 8-character verification code (e.g. A3B7-K9M2) to test and verify the live cloud document in real time.


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✅ Instant Verification Results
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• ✅ Document Is Current: Seal is authentic and cloud document content is 100% unchanged since sealing.
• ⚠️ Document Has Changed: Seal is authentic, but the cloud document was edited after it was sealed.
• 🚫 Invalid Signature: Seal may be forged or originated from a different key.
• 📌 No Seal Found: Document has not been sealed yet.


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💡 Perfect For
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• Legal & Compliance teams: Keep audit-ready, tamper-evident physical printouts and verify active cloud files.
• Finance & Accounting: Seal invoices, financial statements, and balance sheets.
• HR Departments: Distribute verified employment contracts and policy revisions.
• Academic & Research: Certify published data exports, test results, and grade sheets.
• Clients, Auditors & Viewers: Anyone with view-only access (who cannot see Google's Version History or track changes) can independently verify that the cloud document hasn't been quietly altered.
• Any professional who needs unquestionable proof that an active Google Document matches the original sealed one.


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🚀 Key Features
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• Zero external servers: All cryptographic operations run natively inside Google Apps Script™. Your sensitive document content never leaves Google's secure infrastructure.
• Zero quota usage: No external API limits, no rate limits, no per-document fees.
• Unified Docs & Sheets experience: Same intuitive panel and seamless workflow across both Google Docs™ and Google Sheets™.
• Independent verification for Viewers: Viewers who have no permission to see Google's Version History or track changes can still verify whether a document was edited after sealing.
• Always-free verification: Verification requires NO license and is 100% free for all recipients, viewers, clients, and auditors. Only sealing new documents requires a license.
• QR code + Short Code: Scan with any smartphone camera or enter the human-readable 8-character code.
• UTC Timestamps: Every seal is timestamped in unambiguous Coordinated Universal Time (UTC), avoiding timezone disputes.
• Polished Dark-Mode Panel: Clean, modern Google Workspace™ sidebar UI designed for fast daily workflows.
• 3-day free trial: Full access to document sealing features before purchasing.


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🔒 How It Works Under the Hood (No Jargon)
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Document Sealer calculates a unique SHA-256 fingerprint of your document. If even a single character or number changes, this fingerprint changes completely.

The fingerprint is cryptographically signed with HMAC-SHA256 using your account's secure private key.

The signature and metadata are packaged into a high-density QR code placed in the footer or sheet.

During verification, Document Sealer recomputes the math against the current cloud document to guarantee absolute integrity without sending data over the network.

If a document has been altered in any way since it was sealed, verification detects it immediately.


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📋 What You Get
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✅ Document Sealer — Full Google Workspace™ Add-on
✅ 1 Year License (unlimited document sealing)
✅ Verification is always 100% free — no license needed for recipients or viewers
✅ Full compatibility with Google Docs™ & Google Sheets™
✅ 3-day free trial included
✅ Step-by-step setup and license activation guide
✅ All future updates and improvements included


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⚙️ Requirements
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• Google Account (Personal @gmail.com or Google Workspace™)
• Google Docs™ or Google Sheets™ in any modern web browser (Chrome, Edge, Firefox, Safari)


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❓ Frequently Asked Questions
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Do recipients, clients, or viewers need a license to verify?
No! Verification is 100% free and never requires a license. Anyone with access to the document or holding a printed copy can verify seals at zero cost. Only sealing (creating and inserting new seals) requires an active license or trial.

Can I use this across multiple documents?
Yes! Once activated, your license allows unlimited sealing across all your Google Docs™ and Sheets™.

Does verification require an internet connection?
The QR code and short verification code contain the self-contained cryptographic payload. Verification math runs locally inside Apps Script.

Is my document data ever shared or uploaded?
Never. Document Sealer runs entirely inside your Google account. Only your license key is verified against Gumroad's API once every 24 hours.

What if I lose my license key?
You can retrieve your key anytime at https://gumroad.com/license-key-lookup using the email address you purchased with.

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Document Sealer — Tamper-evident cryptographic document integrity for Google Workspace™.

*Google Docs™, Google Sheets™, Google Apps Script™, and Google Workspace™ are trademarks of Google LLC.*