PDF Password Protector - Add a Password to PDFs

PDF Password Protector for adding open passwords to PDFs

Add a password to a PDF directly in your browser. Upload an unencrypted PDF, enter the password you want readers to use, and download a rebuilt PDF that asks for that password when opened. The file is processed locally with @cantoo/pdf-lib, so the document and password are not uploaded to a server.

How do I add a password to a PDF?

Choose your PDF, type the new password, and click "Add Password." The tool encrypts the document in your browser and immediately downloads a new password-protected PDF file.

Is my PDF uploaded anywhere?

No. The protection process runs in your browser using local JavaScript. Your PDF bytes and password stay on your device, which is useful for private forms, invoices, contracts, statements, and other sensitive documents.

What kind of PDF password does this tool add?

It adds a document-open password. Anyone who opens the protected download needs the password you entered before the PDF reader can display the pages.

Can I use this to change an existing PDF password?

Use the PDF Password Remover first if the PDF already has a password. After you create an unlocked copy, upload that file here and add the new password.

Why would I password protect a PDF?

Adding an open password can help when sending a sensitive document by email, archiving files on a shared device, or giving a small amount of extra access control to forms, statements, records, and drafts.

Will the protected PDF keep the original pages?

Yes. The tool loads the original PDF, applies password protection, and saves a fresh copy with the same pages. File size may change because the protected download is newly written rather than byte-for-byte identical to the source.

Why does the file size change after adding a password?

PDFs contain internal objects, streams, metadata, and cross-reference data. When the PDF is saved again with encryption, those structures can be reorganized, so the protected PDF may be smaller or larger than the original.

What should I do if the PDF cannot be protected?

Make sure the file is a valid, unencrypted PDF. If the document already requires a password or uses an unsupported PDF feature, create an unlocked copy first or export a fresh PDF from the original app.

Can I add passwords to several PDFs at once?

This tool handles one PDF at a time so you can verify the file and password before downloading the protected copy. For other browser-based document workflows, try the Markdown Viewer or Typst to PDF Compiler.

Is a password-protected PDF the same as full document security?

No. A PDF open password helps restrict casual access, but it is not a replacement for careful sharing, secure storage, or end-to-end encrypted delivery when the document contains highly sensitive information.