Digitally Sign PDF
Apply cryptographic digital signature
Lock After Signing
Certify document to prevent changes
This tool processes your files entirely in your browser. Your documents never leave your device.
Input
Drag & drop PDF files here
or Browse Files
PDF, PDF•Max size: 100MB per file
Output
Upload a PDF file
About This Tool
Certify and lock PDF documents with our free online document certification tool. Apply certification signatures that prevent further modifications, creating tamper-evident documents compatible with Adobe Acrobat Reader and all PDF applications.
Certification signatures mark the document as finalized and lock it against changes. Choose certification levels: no changes allowed, form filling only, or form filling and annotations. Compliant PDF readers display warnings if locked documents are modified.
All document certification happens locally in your web browser. Your documents and signing credentials never upload to external servers, ensuring privacy for finalized contracts, official documents, and certified records.
Perfect for finalizing official documents, certifying completed contracts, creating tamper-evident records, or marking documents as authoritative versions. Note: Lock enforcement depends on PDF readers respecting the certification flag—not all applications enforce document locks. Works with your digital signing certificate.
Frequently Asked Questions
- Is Lock After Signing free?
- Yes, completely free with no hidden costs, subscriptions, or usage limits. All tools are available at no charge.
- Is it safe to use Lock After Signing?
- Yes, 100% safe. All processing happens locally in your browser. Your files are never uploaded to any server and never leave your device.
- What is the maximum file size?
- You can process files up to 100MB. Since everything runs in your browser, processing speed depends on your device.