How to Password Protect a PDF for Free
You need to lock a PDF before sending it. Here are every free method available — online tools, Mac's built-in Preview, LibreOffice, and more.
Method 1: Online tool (any device, no install)
Go to quicktoolshub.org/lock-pdf. Upload your PDF, enter a password, click Lock PDF, and download the protected file. The encryption runs in your browser — nothing is sent to a server. Works on Windows, Mac, iPhone, and Android.
Method 2: Mac Preview (built-in, free)
Open the PDF in Preview (double-click the file). Go to File > Export as PDF. Click the Security Options… button. Check “Require password to open document” and enter a password. Click OK, then Save. The saved file is now password-protected.
Method 3: LibreOffice Draw (Windows/Mac/Linux, free)
Open LibreOffice Draw. Go to File > Open and open the PDF. Then go to File > Export as PDF. In the export dialog, click the Security tab. Enter a password in the “Open password” field. Click Export and save the file.
Method 4: Microsoft Word (if you created the PDF from a Word doc)
Open the original Word document (.docx). Go to File > Export > Create PDF/XPS. Click Options…. Check “Encrypt the document with a password”. Enter a password and click OK. Then click Publish to save the protected PDF.
Method 5: Adobe Acrobat Pro (paid, most features)
Open the PDF. Go to Tools > Protect > Encrypt > Encrypt with Password. Check “Require a password to open the document”. Enter the password. Choose the compatibility level (Acrobat X and later uses 256-bit AES, the strongest standard). Click OK and save.
Which method should I use?
For most users, the online Lock PDF tool is the fastest option — no install, no account, works on any device. Mac users with Preview already installed can use Method 2 without any additional tools. LibreOffice is the best desktop option if you frequently need to protect PDFs.
Regardless of method, use a strong, unique password. A long random string (12+ characters with numbers and symbols) is dramatically harder to crack than a common word or short phrase.
Password protect a PDF now
Upload, set a password, download. No sign-up, no upload to server.
Use Lock PDF →Frequently asked questions
How do I password protect a PDF for free?
Use the free Lock PDF tool at quicktoolshub.org/lock-pdf. Upload your PDF, set a password, and download the protected file. The encryption runs in your browser — no sign-up, no upload, no cost. Other free options include LibreOffice (Windows/Mac/Linux) and Preview on Mac.
Does adding a password to a PDF require Adobe Acrobat?
No. Adobe Acrobat Pro can add PDF passwords, but it requires a paid subscription. Free alternatives include online tools like QuickToolsHub, LibreOffice Draw, Preview on Mac, and Google Chrome's built-in PDF handling. All produce standard encrypted PDFs that open in any PDF reader.
What is the difference between a user password and an owner password?
A user password (also called open password) is required to open and view the PDF at all. An owner password (also called permissions password) controls what recipients can do with the file — whether they can print, copy text, or edit it. Both are stored in the encrypted PDF. Most users only need a user password to control who can read the file.
How strong is PDF password protection?
It depends on the encryption standard. PDF 40-bit RC4 encryption (used in older PDFs) can be brute-forced with modern hardware. PDF 128-bit AES encryption (PDF 1.6+) is significantly stronger. The strength also depends on your password — a long, random password is much harder to crack than a short common word. For highly sensitive documents, use a strong random password of 12+ characters.
Can I password protect a PDF on a Mac without Acrobat?
Yes. On Mac, open the PDF in Preview, go to File > Export as PDF, and click the Security Options button. Enter a user password (to open) and/or an owner password (for permissions). Click OK and save. This is completely free and produces a standard encrypted PDF.
What happens if I forget the password?
If you forget the password for an encrypted PDF, there is no standard way to recover it. Password recovery tools exist but they use brute-force methods and only work on weak passwords. Always store your PDF passwords in a password manager. If you are the document creator, keep an unencrypted backup of the original file.