Password Protect PDF
Encrypt PDF online, unlock protected PDFs you own, or remove known passwords.
Drop files here or click to upload
Max 100 MB
PDF encryption adds a password requirement to a PDF, preventing anyone without the password from opening it. It is the standard way to share sensitive documents — legal contracts, medical records, financial statements — over channels that are not fully secure themselves. PDF supports two password types: a user password (required to open the file) and an owner password (required to modify the file, e.g., print, copy text, or extract pages). This tool applies user password protection, which is the more common requirement. Decryption works in reverse: given a PDF with a password, the tool rebuilds it as an unencrypted PDF that anyone can open. You need to know the password to decrypt; the tool cannot break unknown passwords. Encryption and decryption both run in your browser — nothing is uploaded.
Last reviewed: July 2026
What is this?
PDF encryption has evolved through several standards. The oldest (PDF 1.3) used RC4 with 40-bit keys, which is now trivially breakable and only relevant for reading legacy files. RC4 128-bit (PDF 1.4-1.5) provides stronger protection but is still considered cryptographically weak by modern standards. AES-128 (PDF 1.6) and AES-256 (PDF 1.7+) are the current secure standards used by professional PDF software. This tool uses RC4 128-bit for encryption — sufficient for casual protection against curious viewers but not for highly sensitive data. For enterprise-grade encryption, use desktop tools like Adobe Acrobat Pro that support AES-256.
How to use this tool
- 1Choose the operation: Encrypt (add a password) or Decrypt (remove a password from a file you can open).
- 2For encryption, pick a strong password. Longer is better than shorter — a 12-character random password is stronger than a 20-character dictionary word. Store the password somewhere safe; without it, the file cannot be recovered.
- 3For decryption, enter the correct password. If you enter the wrong password, decryption fails. If you have lost the password, this tool cannot help — password recovery requires brute-force cracking, which is not offered here.
- 4Click Process to apply the operation. Download the resulting PDF. For encryption, only people with the password can open it. For decryption, the output is a standard PDF anyone can read.
Tips & best practices
- Use a password manager to generate and store passwords. Do not use passwords you use elsewhere — if this PDF is shared and leaked, the password becomes public.
- The tool applies RC4 128-bit encryption. This is sufficient for casual protection (nosy coworkers, accidental exposure) but not for highly sensitive data. Use desktop tools like Adobe Acrobat Pro for AES-256 encryption.
- Some PDF viewers may prompt for the owner password to allow printing or copying, even if the user can open the file. The tool sets both to the same value for simplicity.
- Do not encrypt PDFs you plan to modify further with other tools. Merge, split, compress, and OCR all require decryption first.
- Passwords are case-sensitive. 'Password' and 'password' are different. Special characters and spaces are allowed but may cause issues on some older PDF readers — test the output before sharing.
Common use cases
- A lawyer encrypting a settlement agreement before emailing it to opposing counsel to prevent forwarding.
- A doctor sharing an X-ray report via patient portal, encrypted with a password the patient already knows.
- An accountant sending a client's tax return with a password based on their date of birth (a mild but real deterrent to accidental exposure).
- A journalist encrypting source documents before storing them in a shared team folder, so only teammates with the password can access.
- An HR manager encrypting termination letters or performance reviews before emailing them to affected employees.
- A researcher removing the password from a legacy encrypted PDF they own so they can run it through other tools like OCR or Extract Text.
Technical notes
- The tool uses pdf-lib-plus-encrypt for encryption and pdfjs-dist for decryption workflows.
- Encryption method: RC4 128-bit. This matches PDF 1.4-1.5 standard and works with all mainstream PDF readers (Adobe Acrobat 6+, Chrome, Firefox, Safari).
- Both user password and owner password are set to the same value in this tool for simplicity. Advanced use cases (different user vs. owner passwords) require desktop software.
- The tool cannot recover forgotten passwords. If you enter the wrong password during decryption, the operation fails — password cracking is not offered.
- Decrypted output has the same page count, structure, and content as the source. Only the encryption dictionary is removed.
- Encrypted PDFs cannot be modified by browser-based tools (merge, split, compress, etc.) until they are decrypted first.
Private by design
This tool runs in your browser. Your file is not uploaded to our server while using the tool.
Limitations
- Encryption strength is RC4 128-bit — adequate for casual protection but not for highly sensitive data. Use AES-256 via desktop PDF tools for confidential documents.
- Password recovery is not supported. If you forget the password, the file cannot be opened.
- Some PDFs use per-file permissions (e.g., 'no printing allowed') that are not fully replicated by this tool. It focuses on the open/no-open distinction.
- Very old PDFs (PDF 1.3 with RC4 40-bit) can be decrypted but not re-encrypted with the same weak standard — the tool always outputs RC4 128-bit.
- AES-encrypted PDFs (typically created by newer versions of Adobe Acrobat with AES-256) may not decrypt cleanly if the encryption uses advanced features not supported by pdfjs-dist.
- Certificate-based encryption (X.509 certificates instead of passwords) is not supported. Only password-based encryption is handled.
Frequently Asked Questions
What encryption strength does this tool use?
RC4 with 128-bit keys. This is standard PDF encryption (PDF 1.4-1.5 level) and is supported by all mainstream PDF readers. It provides adequate protection against casual access but is not considered cryptographically strong by modern standards.
Can I encrypt with AES instead of RC4?
Not currently in the browser. AES-128 and AES-256 encryption require desktop PDF tools like Adobe Acrobat Pro. This tool focuses on browser-based encryption using the widely-supported RC4 128-bit standard.
Can I recover a forgotten password?
No. The tool cannot break unknown passwords. Password recovery requires brute-force cracking, which is computationally expensive and not offered here. Keep passwords safe.
What is the difference between user password and owner password?
User password protects opening the file. Owner password protects modifying it (printing, copying, extracting). This tool sets both to the same value for simplicity. Advanced use cases requiring different passwords need desktop tools.
Can I use this to remove a password from a PDF?
Yes, if you know the password. Choose Decrypt, enter the password, and the tool rebuilds the PDF without encryption. The output has the same content but is now openable by anyone.
Are password-protected PDFs safe to send via email?
Reasonably safe for casual protection. Anyone with access to the email would still need the password. For highly sensitive documents, use end-to-end encrypted channels (Signal, secure file transfer) instead of relying solely on PDF encryption.
Which PDF readers can open encrypted PDFs?
All mainstream ones. Adobe Acrobat (all versions since 6.0), Chrome's built-in viewer, Firefox's viewer, Apple Preview, and every mobile PDF reader support RC4 128-bit. Very old readers (pre-2003) may not.
Do I need to enter both a user and owner password?
No. This tool asks for one password and uses it for both user and owner. If you need different user vs. owner passwords, use Adobe Acrobat Pro or another desktop tool.
Is the password uploaded to a server?
No. The password stays in your browser memory only. Encryption and decryption both run locally via pdf-lib-plus-encrypt and pdfjs-dist. When you close the tab, the password is gone.