How to password protect a PDF before you email it

Open Protect PDF, choose the file, and type a password under Password to open. The locked copy is made as you type and checked straight away; press Download to save it. Anyone opening the new file has to enter the password first.

Steps

1. Open Protect PDF and drop the PDF on the box, or click to choose it.
2. Type a password under Password to open. Use the eye button to see what you typed.
3. Optional: under Allow without the permissions password, tap Printing, Copying text or Editing to turn it off, then set a separate Password to change permissions.
4. Press Download. Your original file is left as it was.

What the protection does

The PDF is encrypted with AES-256, the strongest method the PDF format defines. Without the password, the pages, text and images in the file are unreadable, not just hidden. After writing the file, the tool reads it back to confirm three things: it refuses to open without a password, it opens with yours, and it carries the permissions you chose.

AES-256 PDFs open in current desktop PDF readers, browser PDF viewers and the built-in viewers on phones and computers once the password is typed.

Open password and permissions password

The two must be different. If they were the same, anyone who can open the file could also lift the restrictions.

Restrictions on printing, copying and editing are honoured by mainstream PDF readers, but they are instructions to the reader app rather than encryption of their own. For anything truly private, rely on the open password.

Sharing a protected PDF sensibly

• Send the password a different way from the file. If the PDF goes by email, send the password by text message or say it on a call. A password in the same email protects nothing from someone who reads that email.
• Pick something long. Several unrelated words are easier to type and harder to guess than a short mix of symbols. The limit is 128 characters.
• Keep a copy of the password. It cannot be recovered if it is forgotten, by this tool or anyone else. Keep your unprotected original too.

Before you lock it

Locking is usually the last step. Do these first, because most tools need the file unlocked:

• Remove pages the recipient should not see with Delete PDF pages.
• Mark who the copy is for with Add watermark to PDF.
• Check the author and other hidden details with PDF metadata.

Troubleshooting

"This PDF already has a password." Remove the old one first with Unlock PDF, using the password you know, then add the new one here.

"Use a different password from the one that opens the PDF." The permissions password has to differ from the open password.

"This file couldn't be read as a PDF." Check that it is a PDF and not damaged; Repair PDF may help.

Questions

How strong is the encryption?

AES-256, the strongest encryption the PDF format offers. Without the password, the file's contents cannot be read.

Can I stop people printing or copying text?

Yes. Turn off Printing or Copying text and set a permissions password. Mainstream readers honour these rules, but treat the open password as the real protection.

What if I forget the password?

It cannot be recovered. Store it where you will find it again, and keep your original file.

Is my PDF uploaded to add the password?

No. The encryption runs in your browser. The file and the password never leave your device.