Protect PDF

A PDF often carries more than it should when it leaves your hands: a salary slip, a Form 16, a bank statement, a rent agreement, an offer letter, a medical report or a scanned ID. Email gets forwarded, chat apps keep copies, and shared drives are opened by people you never meant to include. A password means the file shows nothing until the person you send it to types it, so share the password by a different route, such as a phone call or SMS, not in the same email.

PDFGuard uses AES-256, the security handler defined in PDF 2.0 and used by Adobe Acrobat for its highest setting. The whole content of the file, text, images and attachments, is encrypted, not just hidden. Every current reader opens it: Adobe Acrobat and Reader, Chrome, Edge, Firefox, Preview on Mac and iPhone, and Android PDF apps. Older 40-bit and 128-bit RC4 settings are weak and are not offered here.

Restrictions are a second, separate layer. The open password keeps strangers out. The permissions settings tell readers whether the person who opened it may print, copy text and images, or edit, comment and fill forms. Adobe calls this the permissions password. Leave it blank and a long random one is used, so the restrictions cannot be lifted later; type one if you may need to change them. Most readers respect these settings, but they are a request to the reader app, not encryption of the content, so do not rely on them alone for secrets.

The engine is QPDF, a long-established open source PDF library, compiled to WebAssembly. It is about 0.5 MB compressed, loads in the background while you choose the file, and runs in a worker so the page never freezes. A typical file of a few pages is ready in under a second, and a 20 MB scan in a few seconds. After encrypting, the page opens the new file with your password and confirms AES-256 before it offers the download.

The PDF and the password stay on this device. The file is encrypted by code running in this tab and handed straight to your browser as a download. Nothing is uploaded, nothing is saved, there is no account and no watermark. Sites that protect PDFs on a server receive your unprotected file first, which defeats the point for private documents.

Because nothing is stored, a forgotten password cannot be recovered by this page or anyone else. Keep a note of it. A PDF that already has a password must be unlocked with the known password first, using Unlock PDF. Adding a password to a digitally signed PDF changes the file, so the signature will no longer verify; keep the signed original.