Protect PDF

Lock your document with a password. Free, no upload. 1 GB max · Up to 1 GB · Processed locally, never sent to a server.

You have to send a payslip, a bank statement or a contract by email, and you want a password to be asked for on opening. Protect PDF puts up that barrier: the file it produces will no longer display in Acrobat, Preview, Chrome or a phone reader without the key you chose.

The tool does not simply hang a padlock on your original file. Every page is first rendered by PDF.js into a canvas at twice display resolution, converted to JPEG, then placed by jsPDF into a brand-new document that takes the dimensions of the source page. The encryption is applied at the moment that new document is created, not bolted on afterwards.

That machinery has one direct consequence, better known before you click: the text of the protected document is no longer text, it is an image. It can no longer be selected, searched, or read out by a screen reader. In exchange you get a locked file without going through an online service where your bank statement and its password would both land on someone else’s machine.

How to use it

  1. Drop in the PDF to lock The source document has to open without a password. If it is already encrypted, PDF.js stops and asks you to unlock it before anything else happens.
  2. Type the opening password The field is masked and refuses any entry shorter than four characters. Write that password down somewhere else: there is no recovery mechanism here.
  3. Choose the image quality High corresponds to a JPEG at quality 0.85 and Medium to 0.70. Take High for a document headed for a printer, Medium for an attachment you need to keep small.
  4. Click Run The bar reads “Encrypting page 3 / 12” and advances page by page. Processing time grows in proportion to the page count.
  5. Collect the -protege.pdf file The result carries a note saying that opening is password protected. Open it once to check the key before you pass it on to your recipient.

Opening password and permission restrictions

The password you type is written both as the user password and as the owner password. The first blocks opening: without it, a compliant reader refuses to display a single page. The second governs the permissions, and the document comes out with printing allowed, and copying, modification and annotation denied.

The distinction matters. An opening password rests on encryption: the content really is scrambled inside the file, and without the key there is nothing to display. A permission restriction is only a flag that software is supposed to honour by convention; plenty of software ignores it, and removing it takes no computation at all. Since the owner password here is identical to yours, whoever you give the opening key to also holds what is needed to lift those restrictions.

What a PDF password protects, and what it does not

The PDF format has been through several generations of encryption. The one jsPDF uses is the oldest: RC4 on a 40-bit key derived with MD5, which the file declares through the /V 1 and /R 2 entries. This is neither AES-128 nor AES-256, and a 40-bit key space can be walked through by brute force on ordinary hardware. The lock discourages a curious colleague; it does not hold against someone properly equipped.

Nor does it protect against the most banal leak of all. Once the document has been opened by a legitimate recipient, nothing stops a screenshot, a reprint, or a forward of the file with the password in the same message. The four-character minimum is a technical guard rail, not a recommendation: a long passphrase is better, and it should travel by a different channel from the file it opens.

For a document whose disclosure would genuinely expose you, health data or material covered by professional privilege, the sensible reflex remains an AES-encrypted archive or an end-to-end encrypted messaging service.

What the document loses on the way

Rebuilding the pages as images preserves appearance and nothing else. The following do not survive the operation:

The size often goes up rather than down: a PDF of pure text weighs very little, and the same pages as JPEG weigh noticeably more. The Medium quality narrows that gap when the file has to fit inside an email attachment.

When this tool is the wrong choice

If the document has to stay usable, rasterisation gets in the way more than it helps: a form to be filled in, or a report someone will search for keywords, loses its point once it has been turned into images.

If your aim is to prevent printing or copying while letting the document open freely, this page does not fit either: it requires an opening password and offers no mode where that field could be left empty.

Frequently asked questions

I lost the password. How do I recover my document?

You cannot, not from this page. Neither the key, nor the file, nor any trace of the operation is kept. Always hold on to the unprotected original on your side: it is the only backup there can be.

Does the password travel anywhere?

It is typed into a field on the page, used by jsPDF to derive the key, then forgotten when the tab closes. Neither the key nor the PDF go out over the network; the only request made fetches the jsPDF library from this site’s own server.

Can I sign a document after protecting it?

No, and the order matters. The signing tool relies on pdf-lib, which cannot open an encrypted PDF. Sign first, protect afterwards.

Why is my text no longer selectable?

Because the pages are converted to JPEG before being encrypted. The reader shows a faithful image, but there are no characters left in the file. To get that text back, the OCR tool can read it out of those images.

Will the recipient need any particular software?

No. This encryption belongs to the first generation of the PDF standard and is still recognised by every common reader, including the viewers built into Chrome, Edge, Safari and phones.

Why is printing still allowed?

That is a deliberate setting. A document that cannot even be printed becomes unusable for a legitimate recipient, while the flag stops no software that has decided to ignore it. Copying, modification and annotation are marked as denied.

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