Password Protect PDF
Add password encryption to a PDF directly in your browser. Drop in a file, set a password (with confirmation), optionally restrict printing, copying and editing, and download an encrypted copy. Encryption is performed by the @cantoo/pdf-lib library — a fork of pdf-lib that supports true PDF password protection (RC4/AES) — entirely on your device. Your PDF and password never leave this tab.
How to use
- 1
Upload your PDF
Drag a non-encrypted PDF onto the dropzone (max 250 MB). If the file is already password-protected, decrypt it first — this tool cannot re-encrypt an already-encrypted file.
- 2
Set a strong password
Enter the password twice. The strength meter shows entropy and an estimated offline crack time. Use at least 12 mixed characters — store it in a password manager before downloading.
- 3
Choose permissions (optional)
Restrict printing, copying, editing, annotating, form filling, page assembly or screen-reader access. These apply only when the file is opened with the user password; the owner password (same value here) always has full access.
- 4
Encrypt and download
Click Encrypt PDF. The file is encrypted locally with @cantoo/pdf-lib and saved as a standard password-protected PDF. Download it and verify in any PDF reader.
Common use cases
- Protect a tax form, contract or payslip before emailing it.
- Lock down a draft document so collaborators can read but not edit or print it.
- Add a password to a scanned ID or medical record for secure storage.
- Restrict copying and printing of a sensitive internal report shared externally.
Limitations
- The user and owner passwords are set to the same value. To use different owner/user passwords, encrypt the file in Acrobat or qpdf afterwards.
- PDF permission flags (printing, copying, etc.) are honoured by well-behaved readers but are not cryptographically enforced — some tools ignore them entirely. They are a deterrent, not a hard guarantee.
- The library chooses between RC4 (PDF 1.4–1.6) and AES (PDF 1.7+) based on the source document. For maximum compatibility with modern readers, the output is generally PDF 1.7 or 2.0 with AES.
- Files larger than 250 MB are rejected to keep the browser tab responsive. For very large PDFs, use a desktop tool such as qpdf or Acrobat.
- There is no password recovery. If you forget the password, the file is unrecoverable. Store it in a password manager before deleting the original.