Security
Password Protect PDF
Add a password to your PDF in your browser. Nothing is uploaded.
What password protection does
This tool creates a PDF that asks for a password when someone tries to open it. QPDF runs as WebAssembly inside your browser and writes real PDF encryption into the downloaded file. The password and PDF bytes are not sent to PDF Plain.
Password protection is useful when you must email or store a document outside a system you fully control. It reduces accidental access, but it is not a substitute for secure sharing, access logs, or identity verification. Anyone who knows the password can open the file and may be able to copy or redistribute its contents.
Choose and share the password carefully
- Use a long, unique passphrase rather than a short word or reused account password.
- Send the password through a different channel from the PDF, such as a phone call or separate message.
- Test the downloaded PDF in the reader your recipient uses before deleting the unprotected original.
- Keep a secure copy of the password. PDF Plain cannot recover or reset it.
For sensitive details that must not appear in the file at all, use Redact PDF before adding a password.
FAQ
Can PDF Plain recover my password?
No. Store it safely before sharing the protected PDF.
Is this real encryption?
Yes. The PDF is processed by QPDF running in WebAssembly in your browser.
Are files uploaded?
No. The file stays on your device.
Can I protect an already encrypted PDF?
Unlock it first, then apply a new password.
Does a password stop screenshots or copying?
No. A person who can open the document can still capture or redistribute what they see. Use redaction to permanently remove information that should not be disclosed.
Why should I test the protected PDF?
PDF readers do not all handle every encrypted file identically. Open the result in your normal reader and confirm the password prompt before sharing it.
Can I remove the password later?
Yes, if you know it. Use Unlock PDF to create a new unprotected copy in your browser.