Password-Protect a PDF

Why password-protect a PDF

Email attachments get forwarded, cloud links get shared and laptops get lost. If a PDF contains salary details, medical results, tax returns, ID scans or client data, adding a password means only people who know it can open the file. Many organisations require password-protected attachments for personal data, and it is a simple habit that limits the damage of a mis-sent email.

This protect PDF tool encrypts the whole document with AES-256 using qpdf, a well-established open-source PDF engine, running in your browser.

How it works

PDFs support two kinds of passwords:

• An open password (user password) – needed to open and read the file. Without it, the content is encrypted and unreadable.
• An owner password with permissions – controls what readers allow once the file is open, such as printing or copying.

This tool sets the open password you choose, which encrypts the content, and applies the permissions you tick:

• Block printing – readers will not offer to print.
• Block copying text and images – selecting and copying content is disabled.
• Block editing (on by default) – discourages changes such as adding or removing pages and editing text.

Permissions are honoured by mainstream PDF readers, but they are a policy, not encryption: some tools ignore them. The open password is what actually protects the content.

Choosing a good password

The tool requires at least 6 characters, but longer is far stronger. A passphrase of four or five random words – for example copper lantern orbit meadow – is easy to type and very hard to guess. Avoid names, birthdays and the recipient’s email address.

Send the password separately from the PDF: if you email the file, share the password by phone, text message or a different channel. Sending both in the same email defeats the purpose.

Step by step

1. Add the PDF.
2. Enter the password in Password and Confirm password. If they do not match, the tool tells you.
3. Choose restrictions, if any.
4. Press Protect PDF. The status shows “Encrypting with AES-256…” and then offers the download.
5. Open the downloaded file and enter the password once to make sure it works.
6. Keep the original in a safe place, or note the password in a password manager.

The tool warns you plainly: there is no way to recover a forgotten password, because the password never leaves your device and we never see it.

Which readers support AES-256 PDFs?

All current PDF software: Adobe Acrobat and Acrobat Reader, Apple Preview and the iPhone/iPad Files app, Google Chrome, Microsoft Edge, Firefox, Android’s built-in viewers and most mobile PDF apps. Very old software (from before about 2008) may not open AES-256 files.

Removing or changing a password later

To remove protection, or to change the password, use Unlock PDF with the current password, then protect the unlocked file again with a new password if you wish.

Combine with other tools

• Shrink first: encryption does not reduce size, so compress large scans with Compress PDF before protecting them.
• Sign first: add a signature with Sign PDF, then protect the signed version.
• Mark it confidential: add a visible “CONFIDENTIAL” stamp with Watermark PDF.

Read our guide How to password-protect a PDF for more on what a PDF password does and does not protect against.

Privacy

Your file and your password stay on your device. The PDF is read into the browser tab, encrypted there and handed back to you as a download. Nothing is uploaded, logged or stored.