Sending a document that should not be read by everyone who receives the email is an ordinary requirement — a contract, a bank statement, an ID scan, a salary letter, a set of results. Password protecting a PDF is the usual answer, and most people assume it requires paid software.
It does not. Every platform has a free method, several of them built in. What varies is how secure the result actually is, and that distinction matters more than the convenience.
This guide covers the methods that work, ranked roughly by how much you should trust them, and explains the difference between the two kinds of PDF password — which is the thing almost nobody knows and which determines whether your protection is real.
The two kinds of PDF password
This is the important part, so it comes first.
A user password (sometimes called an open password) is required to open the document at all. Without it, the file cannot be read. The content is genuinely encrypted.
An owner password (or permissions password) allows anyone to open and read the file, but restricts printing, copying or editing.
Owner password restrictions are not real security. The document is not meaningfully encrypted, and a great many tools will remove those restrictions in seconds. If you have applied an owner password and believe the content is protected, it is not.
If you want the content to be private, you need a user password. Everything below refers to that unless stated.
Mac: built in and genuinely good
macOS has this built in and it takes about fifteen seconds.
Open the PDF in Preview, then File, Export. In the export dialogue, tick Encrypt, enter a password and confirm it, then save.
Alternatively, from almost any application: File, Print, then the PDF dropdown at the bottom left, choose Save as PDF, click Security Options, and set a password to open the document.
This produces properly encrypted output. No extra software, no upload.
Windows: no built-in option, but free routes exist
Windows has no built-in PDF encryption, which surprises people. The Microsoft Print to PDF driver does not offer password protection.
If you have Microsoft Word, this is the easiest path. Open or paste your content into Word, then File, Save As, choose PDF as the type, click Options, and tick Encrypt the document with a password.
LibreOffice is free and does the same thing well. Open the document, File, Export as PDF, go to the Security tab, click Set Passwords, and set an open password. LibreOffice also lets you set permissions separately, and it is clear about the distinction.
7-Zip is a different approach worth knowing. Rather than encrypting the PDF itself, put it in an encrypted archive: right-click the file, 7-Zip, Add to archive, choose the zip or 7z format, set a password, and — importantly — tick Encrypt file names if using 7z. AES-256 encryption, genuinely strong, and the recipient needs 7-Zip or a compatible tool to open it.
iPhone and iPad
The Files app can do this natively.
Open Files, find the PDF, long-press it, and choose Lock PDF. Enter a password. The file is encrypted in place.
To remove protection later, long-press and choose Unlock PDF, entering the password.
If you need to create the PDF first, most apps can print to PDF via the share sheet, after which you can lock it in Files.
Android
Android has no universal built-in option, and it varies by manufacturer.
Some file managers and PDF apps include the feature. Google Drive can open and view but does not encrypt.
The most reliable free route on Android is a well-known PDF app with the feature, or the archive approach: use a file compression app to place the PDF in a password-protected zip. As on Windows, this is genuinely strong if the app uses AES encryption.
Be selective about which app you install. This is a category with a large number of low-quality applications requesting excessive permissions, and you are handing them a sensitive document.
Online tools: convenient, and think before you use them
There are many websites offering free PDF password protection. They work, and they are the easiest option when you have no suitable software.
The obvious caution: you are uploading your document to somebody else’s server. For a restaurant menu, that is irrelevant. For a bank statement, a passport scan, a contract or anything containing personal data, it is a genuine consideration — precisely the documents people most often want to protect.
If you use one, prefer a well-established service, check whether it states that files are deleted after processing, avoid it entirely for identity documents and financial records, and never use one on a shared or public computer.
Given that Mac, Word, LibreOffice and 7-Zip all handle this offline for free, the online route is rarely the best choice for anything sensitive.
Choosing a password that is worth setting
A weak password on an encrypted PDF is a locked door with the key under the mat.
Length matters more than complexity. A passphrase of several unrelated words beats a short string of symbols.
Do not reuse a password you use elsewhere.
Never send the password in the same message as the file. This is the most common mistake by a wide margin. If the email is intercepted or forwarded, both halves travel together. Send the file by email and the password by a different channel — a phone call, or a separate message.
Avoid predictable choices such as the recipient’s name, a date of birth, or the document reference.
Removing protection
If you have the password and want to remove it: on Mac, open in Preview with the password and export without encryption. In Word or LibreOffice, open and re-export without a password. On iPhone, long-press in Files and choose Unlock PDF.
If you have lost the password, there is no legitimate shortcut. Properly encrypted PDFs cannot be opened without it, which is the whole point. Tools claiming to recover strong passwords are either attempting brute force, which is impractical against a good password, or are removing owner-password restrictions and calling it recovery.
A quick comparison
Method
Cost
Real encryption
Notes
Mac Preview
Free
Yes
Easiest on Mac
Microsoft Word
Included if you have it
Yes
Straightforward
LibreOffice
Free
Yes
Best free desktop option
7-Zip archive
Free
Yes, AES-256
Very strong; recipient needs a tool
iPhone Files
Free
Yes
Built in, quick
Online tools
Free
Usually yes
You upload the document
Owner password only
—
No
Restrictions, not protection
The short version
Use a user password, not an owner password — the second restricts printing and copying but does not protect the content, and is trivially removed.
On Mac, use Preview’s Export with Encrypt. On Windows, use Word or LibreOffice, or put the file in an AES-encrypted 7-Zip archive. On iPhone, long-press in Files and choose Lock PDF.
Avoid online tools for anything sensitive, since the document goes to somebody else’s server. And whatever method you choose, send the password through a different channel from the file — doing both in one email defeats the entire exercise.
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