What Are PDF Security Tools?
PDF security is not one feature. Password encryption, decryption, visible signatures, redaction and document comparison solve different problems. This category separates those workflows so each tool can explain exactly what it changes. The tools are designed for browser processing: document bytes remain in the page instead of being posted to a conversion server.
Unlock PDF is for a password-protected PDF when you already know an authorized password. It is deliberately not a password-cracking service. Protect PDF applies genuine PDF encryption rather than putting a JavaScript prompt in front of an unchanged file. Sign PDF creates a visible signature mark and clearly distinguishes that from certificate-based cryptographic signing. Redact PDF rebuilds sanitized pages so hidden source text is not simply covered by a rectangle. Compare PDF examines both extracted text and rendered page appearance.
Protect a PDF with a Password
Password protection is useful when a document should require an open password. The Protect tool uses a PDF encryption engine and creates a separate owner password for security settings. Printing, extraction and modification permissions can be configured, but those permissions are viewer-enforced controls rather than unbreakable digital rights management. Strong encryption protects the encrypted file; it cannot stop an authorized recipient from photographing or otherwise reproducing information they can view.
Unlock a PDF You Are Authorized to Open
Removing encryption is appropriate when you own the file or have permission to modify it. The browser asks for the current password, checks it locally, and creates a decrypted copy. No password guessing or automated recovery loop is included. If the password is forgotten, the correct route is to contact the document owner rather than attempt to bypass protection.
Add a Signature to PDF
A visual signature is a handwritten drawing, typed name or uploaded signature image placed on a page. It can be useful for ordinary acknowledgement workflows, but it is not automatically a certificate-backed digital signature and does not itself prove identity. The Sign PDF tool preserves that distinction in both the interface and the exported result information.
Securely Redact Sensitive Information
Secure redaction requires more than drawing an opaque object above existing text. A black overlay may leave the underlying text searchable or extractable. The secure flattened workflow renders each page, paints the redaction into the actual pixels, and creates a new PDF from those sanitized images. The loss of original text, links, forms, bookmarks and signatures is an intentional security tradeoff.
Compare Two PDF Versions
Text comparison and visual comparison answer different questions. Text extraction identifies words or numbers that changed when a usable text layer exists. Visual comparison detects differences in rendered page appearance and therefore also works for scanned documents. Small anti-aliasing differences can appear in pixel comparison, so the result is a document review aid rather than an automatic legal conclusion.
PDF Passwords vs Digital Signatures
Encryption controls access to document contents. A cryptographic digital signature uses a private key and certificate to verify signed bytes and signer identity claims. A visible handwritten image is not equivalent. This release provides reliable visual signing and intentionally omits certificate signing rather than manufacturing an unverifiable security claim.
Browser-Based PDF Privacy
These tools are built for local processing. Passwords, visual signatures, redaction regions and comparison text are application state in the browser and are not sent to an API. Browser memory is still finite, so very large documents can require significant RAM. For security-sensitive work, review the resulting document in a trusted PDF viewer before distributing it.
Choosing the Right Security Operation
PDF security is not one feature. Encryption controls who can open a document, usage permissions express what conforming viewers should allow after opening, signatures place or verify authorship marks, redaction removes information from a new sanitized copy, and comparison helps reviewers understand what changed between versions. Choosing the wrong operation can create a false sense of safety. For example, cropping a page is not redaction, and a visual signature is not a cryptographic certificate signature.
When a file already has password protection, use Unlock PDF only when you know a valid password and are authorized to create an unencrypted copy. When a file needs a new open password, Protect PDF applies genuine PDF encryption rather than putting a password inside metadata or JavaScript. If the concern is confidential material that must not remain recoverable in the output, use Redact PDF instead of drawing a normal black annotation in an editor.
Security and Document Integrity
Security operations can change the byte structure of a document even when the visible pages look the same. Re-encryption, decryption, signing overlays and redaction can therefore affect existing certificate signatures. A cryptographic signature is normally calculated over specific bytes, so changing those bytes can make a viewer report that the signed revision has been modified. Preserve an original signed file when its evidentiary value matters.
Visual signatures are useful for ordinary workflows where a visible mark is sufficient, but they do not prove possession of a private key. This site deliberately labels the Sign PDF output as a Visual Signature. Certificate-based signing is a separate cryptographic subject and is not silently simulated.
What Browser-Local Processing Means
Browser-local processing means the PDF bytes are read with the File API and passed to JavaScript, Canvas, Web Workers or WebAssembly on the visitor's device. A large encrypted or image-heavy PDF may therefore require substantial RAM. The benefit is that the document does not need to be posted to a conversion server. Static library files can still be downloaded like any other website asset; the privacy boundary is that document content, passwords, signature images, redaction areas and comparison text are not sent with those requests.
For organizations with strict supply-chain policies, self-hosting every JavaScript and WebAssembly dependency is preferable. The deployment documentation identifies which dependencies are bundled and which exact-version runtime asset remains a deployment dependency so an administrator can bring it under the same origin before launch.
Password Security Is More Than a Checkbox
A PDF open password should be unique and difficult to guess. Protection is only as strong as the password and the way it is handled. Passwords should not be embedded into URLs, analytics events, localStorage or console logs. The Protect PDF workflow keeps password values in transient browser state and generates a distinct high-entropy owner password with the Web Crypto API.
PDF permission flags such as printing or content extraction are different from encryption secrecy. They are instructions enforced by compliant viewers after a user has access to decrypted content. They should not be described as unbreakable DRM. If the requirement is to keep information secret from someone, control the open password and distribution of the document rather than relying on permission flags alone.
Redaction Requires Destructive Sanitization
Secure redaction has a different goal from ordinary editing. The output should not retain the sensitive source object behind a colored rectangle. The Redact PDF workflow therefore renders each page, paints the selected areas into the pixel data, and builds a fresh PDF from those sanitized images. That process intentionally sacrifices original text selection, links, forms and annotations so the original content streams do not travel into the redacted copy.
Because redaction is consequential, users should inspect every page and keep the source separately. No automated pattern detector can guarantee that every private item has been found. This category favors explicit, reviewable user choices over unsupported claims of automatic or government-certified redaction.
Frequently Asked Questions
Are PDF files uploaded?
No. The security workflows are designed to process document bytes inside the browser.
Is Unlock PDF a password cracker?
No. It requires a password you already know and does not perform guessing or brute force.
Is a visual signature a digital certificate signature?
No. A visual signature is an image or text mark; certificate signing is a separate cryptographic process.
Why is redaction flattened?
Flattening into sanitized page images removes the original page text and content streams from the rebuilt output.
Can PDF permissions be bypassed?
Permission flags are honored by conforming viewers but should not be treated as absolute DRM.
Can I compare scanned PDFs?
Yes for visual differences. Text comparison may be empty unless the scanned document has OCR text.
Does editing affect existing signatures?
Yes. Rewriting, decrypting, protecting, signing visually or redacting can invalidate existing cryptographic signatures.
Can I use these tools on mobile?
The layouts are responsive, but large encryption, redaction and comparison jobs depend on available device memory.