Protect PDF with Password Free
Protect a PDF with a 128-bit password, restrict printing and copying, or unlock a file you already own. Runs entirely in your browser — nothing is uploaded.
Remove the password or restrictions from a PDF. Enter the user password if the file is encrypted — or leave blank to strip restrictions only.
Drop your PDF here
or click to browse — .pdf files only
How to Password-Protect a PDF
- 1Select the Protect PDF tab. Click the drop zone or drag your PDF onto it — the file is read locally and never uploaded.
- 2Enter an open password. Anyone who receives the PDF will need this password to open and view it. Choose something strong — at least 12 characters with a mix of letters, numbers, and symbols.
- 3Optionally set an owner password. This separate password controls permissions. If you leave it blank, a random owner password is generated automatically so that your chosen restrictions are enforced.
- 4Choose permissions: allow or restrict printing, and allow or restrict copying text. These flags are respected by Adobe Acrobat and most desktop PDF readers.
- 5Click Protect PDF. The encrypted file downloads as filename_protected.pdf — share it knowing only recipients with the open password can view it.
How to Unlock a PDF
- 1Select the Unlock PDF tab and upload the password-protected PDF.
- 2Enter the open password if the file requires one to open. If the file has only owner-level restrictions (no open password), leave the field blank.
- 3Click Remove Password. The tool strips the encryption dictionary and re-saves the PDF as filename_unlocked.pdf — fully unrestricted and ready to share or edit.
Encryption Standard Details
| Property | Value | What it means |
|---|---|---|
| PDF version | PDF 1.4 | Compatible with virtually all PDF viewers, including Adobe Reader 5+ |
| Security revision | R=3, V=2 | 128-bit key space; standard PDF security handler |
| Cipher | RC4 (128-bit) | Stream cipher applied to all content streams in the document |
| Key derivation | MD5 × 51 rounds | Password is padded and hashed 51 times to produce the encryption key |
| Owner key | RC4 × 20 rounds | Protects the permission flags from being changed without the owner password |
| Permission flags | Bits 3 & 5 (P integer) | Controls print (bit 3) and copy-text (bit 5) permissions per PDF spec Table 22 |
Tips for Protecting PDF Files
Use a Strong Open Password
A short or common password can be guessed quickly with brute-force tools. Use at least 12 characters combining uppercase, lowercase, numbers, and symbols. A password manager can generate and store it for you.
Record the Password Immediately
If you forget the open password, the file is unrecoverable — there is no reset option. Save the password in a password manager as soon as you create it, before sending the file to anyone.
Send Password Separately
Never send the password in the same email or message as the protected PDF. Use a different channel — a text message, phone call, or separate email — so that intercepting one does not give access to both.
Leave Owner Password Blank
Unless you need to set a specific owner password, leave it blank. The tool auto-generates a random one, which is more secure than a reused or short owner password and ensures your print/copy restrictions are actually enforced.
Permissions ≠ Full Security
Print and copy restrictions are honoured by Adobe Acrobat and most desktop readers, but not by browser-based viewers. For truly sensitive content, consider redacting text rather than relying solely on the copy restriction.
Unlock Before Editing
If you need to edit or merge a protected PDF, unlock it first using the Unlock tab. Attempting to modify an encrypted PDF with most editors will either fail or produce a corrupted file.
Frequently Asked Questions
What is the difference between an open password and an owner password?
An open password (also called a user password) is required to open and view the PDF — anyone without it sees only a password prompt. An owner password controls permissions such as printing and copying text; it does not prevent the file from being opened by someone who knows the user password, but it restricts what they can do with the content. If you only set an open password, anyone who opens the file has full permissions. Setting both gives you fine-grained control.
What encryption standard does this tool use?
The tool applies PDF 1.4 Standard Security (Revision 3, Version 2): 128-bit RC4 stream encryption with MD5-based key derivation (50 rounds). This is the same encryption scheme used by Adobe Acrobat for PDF 1.4–1.6 documents and is supported by virtually every PDF viewer. Files produced by this tool are fully compatible with Adobe Reader, Preview on macOS, Foxit, and other standard readers.
Can I remove a password if I forget it?
No — not with this tool, and not with any honest tool. If you forget the open password, the encrypted content cannot be recovered without it. This is by design: the security model is that only someone with the correct password can decrypt the data. If you need to unlock a PDF you own, the only options are to remember the password, use a specialist recovery service, or check whether you have an unencrypted copy saved elsewhere.
Is my PDF sent to a server when I use this tool?
No. All processing — encryption, key derivation, and decryption — runs entirely in JavaScript inside your browser. Your file bytes never leave your device and are never transmitted over the network. The tool continues to work correctly if you disconnect from the internet after the page has loaded. No logs, no storage, no third-party access.
Do all PDF viewers respect the print and copy restrictions?
Most desktop PDF applications honour the permission flags: Adobe Acrobat, Foxit Reader, and Preview on macOS all enforce them. However, browser-based viewers — notably Chrome's and Firefox's built-in PDF renderers — do not enforce copying restrictions; they display the content regardless. For strong protection against copying, consider redacting or rasterising the PDF in addition to password-protecting it.
What does the "owner password" do if I leave it blank?
If you leave the owner password field empty, the tool automatically generates a random 24-character hex owner password. This ensures that the permission flags you set (restrict printing, restrict copying) are enforced — without a different owner password, any user who knows the open password could use tools like Acrobat to change the permissions. The auto-generated owner password is not shown and not saved; its only purpose is to make your permission restrictions effective.
Will a password-protected PDF work on all devices?
Yes. The PDF 1.4 encryption standard is one of the oldest and most universally supported specifications. Protected PDFs produced by this tool open correctly on Windows, macOS, iOS, Android, and Linux — in Adobe Reader, Apple Books, Google Drive's PDF viewer, and most other applications. The recipient simply needs to enter the open password when prompted.
What is the "Unlock PDF" tab for?
The Unlock tab removes password protection and permission restrictions from a PDF you already own. Upload the file, enter the open password if the file is encrypted, and click "Remove Password". The tool re-saves the document without the /Encrypt dictionary, producing a clean, unrestricted PDF. If the PDF has restrictions but no open password (owner-only protection), you can usually unlock it by leaving the password field blank.