How to Password-Protect Any PDF or Document

You need to email a tax return, share medical records, or send a contract that nobody should intercept and read. Adding a password encrypts the file so only someone with the password can open it. Here is how to do it with free tools.

LibreOffice (Free, Works Offline, Any Platform)

Download from libreoffice.org if you do not have it. Open any document (.docx, .odt, .xlsx, or existing .pdf). Go to File > Export as PDF. In the Security tab, set an “Open password” (required to view the file) and optionally a “Permission password” (controls whether someone can print or copy text from the document).

Click Export and choose where to save the encrypted PDF. The encryption standard is AES-256, the same standard used by banks and government agencies. Without the password, the file contents are completely unreadable, even if someone intercepts it in transit.

LibreOffice works on Windows, Mac, and Linux. No subscription, no internet connection needed.

Microsoft Word and Excel (If You Have Office)

Open the document. Go to File > Info > Protect Document > Encrypt with Password. Type your password, confirm it, and save. The next time anyone opens the file, Word or Excel demands the password before showing any content.

To export directly as a password-protected PDF: File > Save As, choose PDF format, click Options, and check “Encrypt the document with a password.” Enter your password and save.

macOS Preview (Built-In, No Downloads Needed)

Open the PDF in Preview (double-click the file on Mac). Go to File > Export. Check the “Encrypt” checkbox at the bottom of the dialog. Enter a password and save. The new file is password-protected. The original remains unprotected, so delete it if you only want the secured version to exist.

This is the fastest method on Mac: two clicks and a password.

Browser-Based Tools (Smallpdf or iLovePDF)

Go to smallpdf.com/protect-pdf or ilovepdf.com/protect-pdf. Upload your file, type a password, and download the encrypted version. Both services use HTTPS and claim to delete uploaded files from their servers within one hour.

These are fine for non-sensitive documents like event invitations or shared project files. For anything containing social security numbers, bank account numbers, medical records, or financial data, use an offline tool like LibreOffice to ensure the file never leaves your computer.

How to Send the Password Safely

Never put the password in the same email as the file. If someone intercepts the email, they get both the file and the key to open it, defeating the entire purpose.

Instead, send the encrypted file by email and the password by a completely different channel: text message, phone call, Signal, WhatsApp, or in person. This way, an attacker would need to intercept two separate communication channels to access the file.

Even better: agree on a shared password in advance during a phone call or face-to-face conversation. Then send the encrypted file without ever transmitting the password digitally.

Choosing a Strong Password

Use at least 12 characters with a mix of uppercase, lowercase, numbers, and symbols. Or use a passphrase: four random words like “granite-bicycle-mango-telescope” are both strong and memorable. Avoid birthdays, pet names, children’s names, and anything guessable from your social media.

If you use a password manager like Bitwarden, generate a random password and share it through the password manager’s secure sharing feature.

Removing Password Protection Later

In LibreOffice, open the protected PDF with the password, then re-export it without checking the encryption option. In Word, go to File > Info > Protect Document > Encrypt with Password, clear the password field entirely, and save. The file becomes unprotected again.

Bottom Line

LibreOffice handles password protection for free on any platform. macOS Preview does it natively with two clicks. Microsoft Office handles it if you have a license. Always send the password through a different channel than the file, and use at least 12 characters.