Add password protection to PDF
Encrypt a PDF with a strong password. Set a user password (to open) and an owner password (to change permissions). AES-256 encryption.
Drag & drop a file
or browse from your computer · max 100 MB
We never see or store your password. AES-256 encryption.
Password must be at least 4 characters
Password-protecting a PDF is essential when you're emailing financial statements, sending HR documents to candidates, or sharing draft contracts with limited access. Without encryption, anyone who intercepts or forwards the email can open the file. PDFOnly encrypts your PDF with AES-256 — the same algorithm used by banks and government agencies — so opening it requires the password you set. The result is a standard encrypted PDF that any reader (Adobe Acrobat, Preview, Chrome's PDF viewer) can open with the correct password.
How to protect pdf step by step
- 1
Upload the PDF you want to protect
Drop your PDF on the upload area. We accept any standard PDF up to 100 MB free, 200 MB on Pro. Already-encrypted PDFs need to be unlocked first using our Unlock PDF tool with the existing password.
- 2
Set a strong password
Choose a password at least 12 characters with mixed case, numbers, and symbols. Avoid dictionary words. We never store your password — it's used to encrypt the file and discarded immediately. If you forget it, the file cannot be recovered (that's the point of strong encryption).
- 3
Click Protect and download
We use qpdf to apply AES-256 encryption. The output looks identical to the input but requires the password to open. Download instantly.
Why protect pdf on PDFOnly
AES-256, not weaker variants
Some online tools default to RC4 40-bit or AES-128. We use AES-256 by default — the same standard required for protecting top-secret government documents.
Standard encryption, not proprietary
The output is a standard encrypted PDF. Any PDF reader (Acrobat, Preview, Chrome, Firefox) can open it with the correct password. No special viewer required.
Password never stored
Your password is held in memory just long enough to encrypt the file, then discarded. We don't log it, don't email it, don't include it in our database.
What people use protect pdf for
A few common scenarios. If your workflow looks like one of these, this tool is a good fit.
Email confidential financial statements
Encrypt before sending tax returns, P&L statements, or bank reconciliations. If the recipient's mailbox is compromised, the attacker still can't open the PDF without the password.
Send HR documents to candidates
Offer letters, salary breakdowns, equity grants — all should be password-protected before they leave your company. Send the password through a different channel (Signal, SMS, phone call).
Lock down legal drafts
Send a contract draft to the counterparty with a password, communicated separately. Prevents accidental forwarding and reduces the risk of leaks.
Protect sensitive reports for board distribution
Quarterly board packets often contain unreleased financial figures. Encryption ensures only board members with the password can open the file.
What you get
- AES-256 encryption (the strongest standard for PDF)
- Set both user passwords (to open the file) and owner passwords (to change permissions)
- Restrict printing, copying, or editing — even with the user password
- Works with any PDF, including scanned documents and form-fillable PDFs
- Free for the basics, no signup required
- Files auto-deleted within an hour, password never stored
Frequently asked questions
What encryption algorithm do you use?
AES-256 with a strong PBKDF2 key derivation. This is the industry-standard for high-security PDF encryption — same algorithm used by Adobe Acrobat for its 'high' encryption level.
What happens if I forget the password?
The file is permanently inaccessible. Strong encryption means no recovery without the password — that's the entire point. Save the password in a password manager (1Password, Bitwarden, etc.) before encrypting anything important.
Can someone bypass the password?
Not within reasonable time/cost. AES-256 with a strong password (12+ characters mixed case + numbers + symbols) is computationally infeasible to brute-force — would take longer than the age of the universe with current hardware. Weak passwords (short, dictionary-based) can be cracked, so use a strong one.
Difference between user password and owner password?
User password (also called 'open password') is required to open the file. Owner password is required to change permissions like printing, editing, or copying — but doesn't prevent opening. Both can be the same. Setting both gives the strongest protection.
Does encryption affect the PDF's content or quality?
No. Text, fonts, images, and metadata are all preserved exactly. Encryption is just a wrapper around the existing PDF structure.
Can I open the encrypted PDF on mobile?
Yes. iOS Files app, Android's PDF viewer, Acrobat Reader Mobile, and any browser PDF viewer can open AES-256-encrypted PDFs with the password.
Is password-protection enough for HIPAA or GDPR compliance?
It's a strong layer but not a complete compliance solution. Compliance also requires audit trails, access logs, breach notification procedures, and other controls. Use password protection as one layer in a broader compliance program.
Ready to protect pdf?
Free to use for the basics. Files are auto-deleted within an hour and never used to train AI.
Open Protect PDF