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BytesPDF
Browser-Local · No Upload — Even for Keys

Sign a PDF — Real Digital Signatures, Locally

Your certificate, your document and your password stay in this tab: a real RSA/SHA-256 signature is computed on your device and appended without touching the original bytes.

Selected PDF Content Stays LocalTime Varies by File and Device

How to Sign a PDF — Real Digital Signatures, Locally in 3 Easy Steps

Browser-local document processing with no application installation required.

1

Drop the PDF

Up to 50 MB. The file stays in this tab for the whole process.

2

Choose Your Identity

Import a .p12/.pfx certificate with its password, or generate a self-signed identity and download the .p12 backup.

3

Sign & Download

Add an optional reason and location, sign, and download the signed PDF — the original bytes are kept untouched as an incremental revision.

Why Use Our Sign a PDF — Real Digital Signatures, Locally Tool?

Current capabilities and limitations, described without universal quality or speed promises.

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Real Cryptographic Signatures

RSA-2048 with SHA-256 in a PKCS#7 detached signature — the same format Acrobat uses. Any change to the file after signing breaks the signature visibly.

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Your Certificate Never Leaves

Import your .p12/.pfx or create an identity here — the file, its password and the PDF are processed in this tab and uploaded to nobody.

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Self-Signed With a Backup

No certificate yet? Generate one locally and download the .p12 backup — the only copy of your signing key, so keep it safe.

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Reason & Location Recorded

Optionally record why you signed and from where — both are locked into the signed data and shown to whoever verifies the file.

Frequently Asked Questions

Get clear answers about data flow, formatting, integrity, and usage limits.

Is this a real digital signature or just an image of my name?
It's real: an RSA-2048/SHA-256 PKCS#7 detached signature appended as an incremental revision, exactly the mechanism Acrobat's 'Digitally Sign' uses. The file carries a hash of its own bytes; if anyone alters even one bit afterwards, verification fails and viewers flag the document as modified.
Why does Adobe show 'validity unknown' for my self-signed signature?
Because Acrobat only fully trusts certificates chained to certificate authorities it already knows. A self-signed certificate proves authorship and integrity mathematically, but Adobe can't confirm who you are against a paid authority, so it shows 'validity unknown' until you add the certificate to your trusted identities. That's an honesty limit, not a defect: the cryptography is the same. Import a CA-issued .p12 here and the green check appears for everyone.
What can I use a self-signed signature for?
Internal approvals, personal records, archiving anything where 'unchanged since I signed it' matters more than third-party identity proof — and for recipients who are willing to trust your certificate. For contracts with strangers, courts or government filings that demand a certified signature, use a certificate from a recognised authority (or a jurisdiction-specific e-sign provider).
What is a .p12 backup and why download it?
It's a standard container holding your private key and certificate, protected here with an empty password for simplicity. Signing later — on this site or in Acrobat — needs that key. The backup is generated on your device and offered once; if you lose it, nobody can sign as that identity again. Treat the file like a key to your house.
Does my certificate or password get uploaded?
No. The entire flow — reading the .p12, deriving the key, hashing the document and computing the signature — runs in this browser tab. There is no server component to upload to, which is the whole point: your signing key is the one credential that must never leave your hands.
Can I sign a PDF that already has a signature?
This tool declines files that already carry a signature, because adding a second signature the wrong way invalidates the first one. Multiple-signature workflows (signer A, then countersigner B) need sequential signing that preserves each prior revision — a good candidate for a future update.

Our Core PDF Tools

Browser-local compress, merge, rotate, rename, inspect, protect and OCR — nothing is uploaded.

📉Compress PDF

Recompress embedded PDF images locally; results and image quality vary

📑Merge PDF

Combine multiple PDFs into a single file, with folder import and auto ordering

🎯Compress to a Target Size

Hit a size limit — 2MB visa, 500KB forms, 25MB Gmail — or get the honest closest result

🔄Rotate PDF

Turn one PDF or a whole batch and save permanent rotated copies

🏷️Rename PDFs in Bulk

Pattern-based batch renaming with a live preview and ZIP download

🧹Remove Metadata

See and scrub hidden author, app and timestamp data before sharing

📋Check Before Sending

Pre-send checklist: size limits, metadata, personal data, page order, redaction risks

🔐Password Protect

AES-256 encryption in your browser with reader permissions — no upload

🖍️Redact Text

True redaction that destroys the text — then verifies it's gone

📇OCR a Scan

Make scans searchable with a local engine — pages never leave the device

🔍Compare Versions

Line-level diff between two drafts, computed locally

🏗️Secure Cleanup

Rebuild pages-only: metadata, attachments, scripts and history dropped

✍️Sign a PDF

Real PKCS#7 digital signatures computed on your device — import a certificate or create one

📄Word to PDF

Convert .docx to a searchable PDF locally — headings, lists and tables reproduced

🗂️Excel to PDF

Print every sheet as a clean grid, locally — dates as dates, no silent cut-offs

🤝Team Workspace

Share activity, not documents — one code puts a feed and notes in front of the team