pdfviz

Protect a PDF with a password

or drop one here

Password protection

Require a password whenever this PDF is opened.

Uses PDF 1.7 AES-128. PDF/A files stay archival and are not encrypted.

Choose a PDF file first.

Add an open password to a PDF so it asks for one before it shows a page. The work happens entirely in this browser tab: the password stays in the tab and never reaches usage data, and the protected copy is opened again with that password before you can download it. Archival PDF/A files are refused, and very large files can exceed what your browser tab can hold.

How to password-protect a PDF

  1. Choose a PDF

    Press Choose a PDF, or drop one on the page. The file stays in this browser tab and is never uploaded.

  2. Leave Protect selected

    Protect is selected when this page opens. Use Unlock only when you want to remove protection using a password you know. A file that is already protected is refused here with a note to choose Unlock instead.

  3. Enter the new password

    Use at least six characters and enter the same password twice. The password stays in this tab and is excluded from usage data and diagnostics.

  4. Protect, verify and download

    The output is opened again. Its pages, page sizes, selectable text and password requirement must pass before Download appears, so the file you save is proven to work.

What an open password does, and what it does not

An open password is the one a reader asks for before it draws a page. Without it the file is encrypted bytes. That is the protection this page writes: a reader must decrypt the file before it can draw a page, so unlike a flag it cannot be skipped.

The other kind is a permissions password, also called an owner password. It marks a file as no printing, no copying or no editing. Those flags are advice. Adobe Reader follows them, other readers may not, and a tool that can open the file can clear them. This page does not offer that layer because it is not real protection. When you need true access control, an open password is the only kind that works.

After protecting a file, you may also want to remove its metadata or run a privacy scan so the file does not leak your name, software or edit history alongside the password-locked content. You can also redact sensitive content before protecting, so the shared file contains only what the recipient needs to see.

When you need to password-protect a PDF

Sending confidential documents by email. Attach the protected file and share the password through a different channel, so a leaked inbox does not expose the content.

Sharing financial or legal records. Tax forms, contracts and bank statements carry personal data. Protect them before they leave your device.

Distributing draft documents. Keep drafts under a password so only reviewers you trust can open them, then unlock and publish the final version when ready.

Archiving sensitive files. Encrypt files at rest by protecting them with a password you control, so a lost laptop or shared drive does not expose the contents.

Sharing medical or insurance records. Protect health documents before sending them to new providers or family members, and share the password through a separate channel.

Distributing exam or assessment materials. Keep test papers under a password until the scheduled start time, so an early leak does not compromise the assessment.

How PDF password encryption works

When you protect a PDF with an open password, the tool encrypts the document using a key derived from your password. Without the password, a reader cannot open it, so the file stays unreadable bytes. With the password, the reader decrypts the content and draws the pages.

This is different from a permissions password, which only sets flags like no-print or no-copy on a file that is already readable. Those flags are advisory and any reader can ignore them. An open password is real encryption - the content is mathematically inaccessible without the key. That is why this tool writes an open password and not a permissions password.

After protecting, the tool reopens the file with the password you entered and checks that pages, page sizes and selectable text match the source. If the encryption broke anything, the check fails and you never see the download. That check is the verified output: the file you save opened with the password you entered.

Questions about password-protecting PDFs

Is my PDF or password uploaded?
No. The PDF, password, encryption operation and verification all stay in this browser tab. No part of the file is sent to a server, and the password never reaches usage data.
What kind of password does this tool add?
It adds an open password, also called a user password. A reader must enter it before it will show any page. It does not add a permissions or owner password, because those flags are advisory and any reader can ignore them.
How strong is the encryption?
The tool protects with AES-128 encryption (PDF 1.7): without the password the file stays unreadable bytes. Archival PDF/A files stay archival and are not encrypted. Use a password of at least six characters, and longer is better.
Can I remove the password later?
Yes. Open the unlock PDF page, enter the password, and download an unprotected copy.
What happens if I forget the password?
There is no recovery path. An open password encrypts the file, and without the password the content cannot be decrypted. Store the password somewhere safe.
Does the protected file look the same?
Yes. The pages, text and layout are unchanged. Only the encryption layer is added. The output is opened again with the password and compared with the source before download.
Is there a file size or page limit?
There is no server-side cap: processing happens in your browser. Very large files are still bound by your browser tab's memory and may take longer on slower devices.
Can I protect multiple files at once?
This page protects one file at a time. For batch workflows, merge the files first, then protect the combined document.

The other pdfviz tools

All of them run in a browser tab like this one, and none of them needs an account.