Protect PDF

How Protect PDF works

Protecting a PDF encrypts its contents with the password you choose. Anyone who opens the file, in Adobe Acrobat, Preview, a browser or a phone, is asked for the password first, and without it the pages cannot be read. The encryption is AES with a 256-bit key, the strongest method the PDF standard offers.

The same password is set as both the open password and the permissions password, so whoever knows it can open, print and edit the document normally. Choose something you can pass on safely, and send the password separately from the file, for example by text message when the PDF goes by email.

Encryption is done by qpdf, an open-source PDF toolkit compiled to WebAssembly, inside this tab. That matters for a tool like this: the unprotected document and the password never travel to a server, which is exactly the risk you are trying to avoid.

There is no way to recover a forgotten password, from us or anyone else, because the file is genuinely encrypted. Keep the original unprotected copy somewhere safe, or note the password where you keep others.

The protected file keeps its name with -protected added, so the unprotected original stays where it was. Everything inside the PDF is encrypted, including the text, images and attachments, and the pages look exactly as before once the password is entered. On an iPhone or Android phone the password prompt appears in the Files app, Mail and every PDF viewer, so the person you send it to does not need special software.

Protect PDF options explained

When to use it

Protect a PDF before emailing payslips, contracts, medical letters, tax documents or anything with personal details, or before putting it in shared storage where people other than the intended reader might open it.

A long passphrase of three or four ordinary words is stronger and easier to share than a short string of symbols.

About the PDF toolkit

Unlock, protect and flatten, and the final step of compression, use qpdf, a long-established open-source PDF toolkit that many desktop programs and servers rely on, compiled to WebAssembly so it runs in this tab. It loads the first time you use one of these tools, about 1.3 MB, and is cached. qpdf works on the internal structure of the file: it can encrypt and decrypt with the PDF standard's own methods, draw form fields into the page, and rewrite objects more compactly, all without re-rendering the pages. Because it runs on your device, passwords and the documents they protect never pass through a server, which is the point of protecting them in the first place.

Protect PDF troubleshooting

"The two passwords do not match"

Type the same password in both boxes. They are hidden, so a single typo is easy to miss.

"already password protected"

The PDF already has a password. Unlock it first with Unlock PDF, then protect it with the new one.

An old program cannot open the file

Very old PDF readers from before about 2008 do not support AES-256. Any current reader, including browsers and phones, opens it.

How to use Protect PDF, step by step

1. Press "Choose a PDF" or drag PDFs onto the box.
2. Set the options if you need to; the defaults suit most uses.
3. Press "Protect PDF". The work happens on your device.
4. Save the result with its download button.

Is it safe to do this online?

With most online tools, "online" means your file is uploaded to a company's server, processed there and kept for a while before it is deleted. Here it is not. The page downloads the tool's code to your browser, and your file is read and processed inside the tab on your own device. It is never sent to TapToConvert or anyone else.

You can check this yourself: once the page and its engine have loaded, turn off Wi-Fi and the tool still works. That also means there is no queue, no daily limit and no file size cap set by a server; the only limit is the memory your browser gives a single tab.