PDF Password Protector
How to password-protect a PDF file, the best free methods available.
Why browsers can't password-protect PDFs
PDF encryption uses AES or RC4 algorithms that must modify the binary structure of the PDF file. JavaScript running in a browser cannot write encrypted binary files without a specialised server-side library (like iTextSharp, PyPDF2, or Ghostscript). Below are the best free alternatives.
Free Ways to Password-Protect a PDF
Microsoft Word
FreeOpen the PDF in Word, go to File → Save As → PDF options → Encrypt with password.
LibreOffice Writer
FreeOpen the file, export as PDF, check 'Encrypt the PDF document' and set a password.
Adobe Acrobat (free viewer)
PaidUse File → Protect Using Password. Requires the full Acrobat version (paid).
PDF24 Tools (online)
FreeA free online tool that encrypts PDFs server-side. Files are processed securely and deleted after.
ILovePDF (online)
FreeUpload a PDF, add a password, download the encrypted file. Files are deleted after 2 hours.
Step-by-Step: Using Word
- 1.Open the PDF in Microsoft Word (Word 2013+ can open PDFs directly).
- 2.Go to File → Save As → Browse.
- 3.In the Save As dialog, choose PDF from the format dropdown.
- 4.Click More Options → then check 'Encrypt the document with a password'.
- 5.Enter your password, confirm it, and save.
- 6.The saved PDF will require the password to open.
FAQ
Is password-protecting a PDF truly secure?
PDF passwords use AES-256 encryption in modern PDFs and are considered secure. However, the security depends entirely on the password strength. Use a strong, unique password.
Can password-protected PDFs be cracked?
With weak passwords, yes, brute-force tools exist. With a strong password (12+ chars, mixed types), it would take billions of years to crack with current computing.
What's the difference between open and permissions passwords?
An open password is required to view the file. A permissions password restricts printing, copying, and editing without preventing viewing.
Will future versions of browsers support this?
The WebCrypto API can encrypt data, but writing a fully standards-compliant encrypted PDF binary in-browser remains very complex. We are exploring it for a future update.