Protect a PDF with a password

How to use Protect PDF

1. Open the PDFThe file is read on this device only.
2. Set the passwordType it twice; optionally set a separate permissions password and restrictions.
3. EncryptDownload the protected PDF and share the password through a different channel.

How strong is it?

The file is encrypted with AES-256 (PDF 2.0 / Acrobat X security handler), the strongest scheme PDF supports. The weak point is the password: use at least 12 characters, ideally a passphrase of several random words. There is no recovery — if the password is lost, so is access.

Open password vs. permissions

The open password is required to view the file. Permissions (printing, copying, editing) are enforced by well-behaved PDF readers; they are a courtesy lock rather than strong protection, because the file can be decrypted by anyone who can open it. A separate permissions password stops casual changes to those settings.

Choosing a password that holds

AES-256 is only as good as the password. A long passphrase of four or five unrelated words is far harder to guess than a short mix of symbols, and easier to read out over the phone. Send the password through a different channel than the file — a text message for an emailed PDF, for example — so one intercepted message isn’t enough.

Need more than one step? The Workbench runs Protect PDF together with other operations on the same file in one go — for example merge → compress → protect.