PDFStack Tool
Protect PDF — Add Password Encryption Free
Add a password to any PDF to prevent unauthorised viewing. PDFStack applies metadata-level protection client-side and saves a protected PDF file you can share with confidence.
Open Protect PDF →
No file uploads
No account required
Free to use
Private & secure
Why password-protect a PDF?
Sensitive documents — contracts, medical records, financial statements, personal IDs — should be password-protected before sharing via email or cloud storage. PDFStack gives you a free way to add that protection without uploading your file anywhere.
How to password-protect a PDF
- 1Open Protect PDF in PDFStack.
- 2Upload your PDF.
- 3Enter a strong password.
- 4Click Protect PDF and download the secured file.
All processing happens locally in your browser — no files are uploaded to any server.
Common Uses
Protecting a contract before emailing, securing a financial document, adding access control to a shared PDF, preventing a form from being edited.
Frequently Asked Questions
How strong is the encryption?
PDFStack applies pdf-lib's built-in protection. For maximum security (AES-256), use Adobe Acrobat or a dedicated encryption tool.
Will the recipient be prompted for the password?
Yes — any PDF viewer will prompt for the password when opening the protected file.
Can I remove the password later?
Yes — use PDFStack's Unlock PDF tool with the password you set.
Is my PDF uploaded anywhere?
No. Protection is applied entirely in your browser.