Protect files before you share them

Which protection fits which job

You want to	Use	What it does not do
Stop anyone without the password from reading a PDF	Password-protect the PDF	Once someone has the password, they have the whole file and can pass both on.
Send several files, or files that are not PDFs, behind one password	Encrypted zip	The person needs an app that opens encrypted zips. File names inside can be visible.
Mark a document as a draft, or as confidential to one reader	Watermark the PDF	A watermark discourages copying. It does not stop it, and it can be cropped out of a screenshot.
Share a document with some names or numbers removed	Redact the PDF	Finds emails, phone, ID and card numbers for you, even on scans, but check every page: names and handwriting can be missed.
Take the file back later, and know whether it was read	Share it as a link	A link needs an internet connection to open.

Why the tools run in your browser

A tool that protects a file should not need a copy of it. These three load their code into the page and do the work on your device: the PDF tool uses qpdf compiled to WebAssembly, the zip tool uses zip.js, and the watermark tool uses pdf-lib, all open-source libraries. You can check this yourself: open your browser's developer tools, watch the Network tab, and process a file. No request carries it anywhere.

Can you password protect a folder?

Not directly, on Windows or on a Mac. Neither puts a password on an ordinary folder, so the usual answer is to put the folder inside something that can be locked.

On Windows 10 and 11

Put the folder in an encrypted zip: add its files to the zip tool, or use the free 7-Zip app, choose AES-256 and set a password. Windows Pro editions also have an option called Encrypt contents to secure data, under the folder's Properties, then Advanced. That ties the files to your Windows account rather than to a password, so it protects them on your own computer but not once they are copied or sent.

On a Mac

Open Disk Utility and choose File, then New Image, then Image from Folder. Pick the folder, set Encryption to 256-bit AES and type a password. The result is a .dmg file that asks for the password every time it is opened. It only opens on a Mac, so for anyone on Windows use an encrypted zip instead.

Everyday habits that protect your files

• Turn on device encryption: BitLocker or Device Encryption on Windows, FileVault on a Mac. A lost laptop then gives nothing away.
• Use a different password everywhere, kept in a password manager, and two-step sign-in on your email and cloud storage.
• Keep a backup that is not always connected, so a mistake or ransomware cannot reach both copies.
• Share less, for less time: send a link with an expiry date instead of an attachment, and delete shares you no longer need.

Protecting the file is half of it

A password or a watermark travels with the file, which is the point, but it also means that once the file is sent you cannot change your mind. If you need to stop access later, change who can open it, or know whether it was opened at all, share it as a link instead of an attachment. Secure file sharing explains the options: a password on the link, an expiry date, view-only, and an email when it is opened.