PDF Logic

Protect & sign

Protect PDF

Lock a PDF with a password so only people you give it to can open the file. The copy is encrypted with AES-256, and the lock is tested before you download it.

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What Protect PDF does

Protect PDF creates an encrypted copy of your document that asks for a password before it opens. The contents are scrambled with AES-256, so without the password the file is unreadable, not merely hidden behind a prompt. The tool then reopens the result to confirm it really does require your password.

Advanced permissions adds an optional second layer that asks PDF readers to restrict printing, copying and editing. Those restrictions rely on each reader app to honor them, so treat them as a firm request; the opening password is what actually keeps people out.

The file check happens in your browser. When you select Protect PDF, the document and your passwords are sent to our server, the copy is encrypted, and the temporary working files are deleted as soon as the job ends. We cannot look a password up for you later.

Is this the right tool?

Good for

  • Emailing pay stubs, tax returns, bank statements or medical letters.
  • Sharing a contract or board paper that only named people should read.
  • Sending a proof that recipients may read but should not print or copy.

Not the right tool for

  • Hiding one paragraph or account number from people who may read the rest. Anyone with the password sees everything.Redact PDF
  • Showing whose copy it is or that it is confidential.Watermark
  • A PDF that already has a password. Remove the old one first, using the password you know.Unlock PDF

How to password-protect a PDF

  1. Choose your PDF

    Select the PDF you want to lock, up to 30 MB. Preview first page lets you confirm it is the right file.

  2. Set the opening password

    Type it under Opening password and Confirm opening password, or select Generate password. Select Copy password and store it somewhere safe before you go on.

  3. Add restrictions if you need them

    Open Advanced permissions, turn on Restrict printing, copying & editing, and set a different Permissions password.

  4. Protect and download

    Select Protect PDF. When the Protection summary appears, select Download protected PDF.

Worked example

Emailing a signed loan agreement

Say you need to email a signed loan agreement to your accountant. It lists your address, income and account numbers.

Choose the PDF and select Generate password, then copy it into your password manager right away. Skip Advanced permissions; your accountant needs to print and annotate the file. Select Protect PDF and attach the protected copy to your email, not the original.

Send the password by a different route, such as a text message or a phone call. If the email is ever forwarded or the mailbox is broken into, the attachment on its own is useless.

Tips for a better result

  • Length beats complexity. A passphrase of four or five unrelated words is easier to type and harder to guess than a short string of symbols.
  • Finish your other changes first. Compressing, merging or numbering a protected file means unlocking it again.
  • Share only the opening password. The permissions password can lift every restriction, so it stays with you.

Protect PDF: questions and answers

How strong is PDF password protection?

The encryption is not the weak point: AES-256 is a published standard, widely used to protect sensitive data, with no known practical way to break it directly. What matters is your password. A short or common one can be guessed by software that tries millions of candidates, so use a long, unique password or let the tool generate one.

Will the recipient need special software to open the protected PDF?

No. Current versions of the common PDF readers and web browsers open password-protected PDFs after asking for the password. Very old PDF software may not support AES-256, so if someone cannot open the file, ask them to try an up-to-date reader.

Do I need to set a permissions password as well?

Only if you turn on Advanced permissions. Most people just need the opening password, which controls who can read the file. The permissions password is for cases where recipients may read the document but should not print, copy or edit it.

Can I take the password off a protected PDF later?

Yes, as long as you still know it. Open the protected copy in Unlock PDF, enter the password, and download an unprotected version. That is also how you change a password: unlock, then protect again with the new one.

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