CornerTools

Protect PDF

Add a password to a PDF with AES-256 encryption, and choose what readers may do, without uploading it.

Drop PDFs here, or

Your files never leave your device

Processed in this browser · up to 50 at a time

Anyone who opens the PDF needs this password. It cannot be recovered if lost, so keep it somewhere safe.

Encryption

Puts a password on a PDF, so only someone who has it can open the file: a payslip or statement before you email it, a scan of an ID before you store it in the cloud. You can also limit what readers may do once it is open, such as printing or copying text. The PDF is encrypted on your device and never uploaded, and neither is the password.

How to use it

Add one or more PDFs; each gets the same password. Type the password and confirm it; Show passwords shows what you typed. Protect PDF saves each file encrypted, named as in payslip-protected.pdf. A PDF that already had a password asks for it first, and the new password replaces it.

  • Restrict what readers can do: clear any of printing, copying text and images, editing, filling in forms to stop readers doing it. Allowing editing also allows filling in forms. The owner password lifts the restrictions; leave it empty and a random one of 22 characters is made and shown with the result, with a button to copy it. It must differ from the open password, which would otherwise lift them too.
  • Encryption: AES-256, the default, or AES-128 for old readers that cannot open AES-256. AES-256 takes a password of up to 127 bytes in any script; AES-128 takes up to 32 Latin letters, digits and symbols, as the PDF format allows.

The options are remembered on this device for next time; the passwords are not.

Frequently asked questions

AES-256 is the strongest encryption the PDF format has, and without the password the contents cannot be read. What decides how safe the file is in practice is the password: a long one that is not a word, a name or a date of birth cannot be guessed, while a short or common one can be found by trying many passwords quickly.
In Adobe Acrobat and most PDF readers, yes: they grey out printing or copying as the file says. But restrictions are a request to the reader rather than encryption of their own: anyone who can open the file can read it, and some programs ignore them. Use them to prevent casual copying, and the open password to keep the file private.
The PDF cannot be opened, here or anywhere else: the password is not stored in the file or sent anywhere, so there is nothing to recover it from. Keep the unprotected original, or the password, somewhere safe.
Only its encryption. The pages, text, images, links, form fields and bookmarks stay as they were. A digital signature stops verifying, as with any change to a signed file; the tool says so when you add one.
No. Your browser reads, encrypts and saves the files on your device; they are not sent to CornerTools or anyone else, and neither is a password you type. To check, open the browser's developer tools at the Network tab and add a PDF: no request carries it. The PDF engine downloads from this site the first time you use it: a download to your browser, not an upload of your file.

See also

  • Unlock PDF — to remove the password again, with the password.
  • Compress PDF — to make the PDF smaller first, for an email attachment.
  • Watermark PDF — to stamp a word such as CONFIDENTIAL on the pages.