How to password protect a PDF — 8 ways, and what each one actually protects

Every practical way to put a password on a PDF, on Mac, Windows, iPhone, Android and the command line — with the encryption strength each one uses, and the two cases where a password on the file is the wrong tool.

22 September 2026 · How to

There are two different things people mean by "password protect a PDF", and picking the wrong one is why so many of these guides end in disappointment.

Encrypting the file puts a password inside the PDF itself. Nobody can read the bytes without it — not your mail server, not the person you forwarded it to, nobody. The password travels with the file forever.

Protecting the delivery puts the password in front of a link. The file sits somewhere; the address asks for a password before it shows anything. You can change the password afterwards, take it away entirely, and see who opened it.

Encrypting the file is right for an archive, an attachment, or anything that has to survive being emailed. Protecting the delivery is right for anything you are sending to someone now and may need to revise, revoke, or follow up on. The eight methods below are split accordingly.

The short version

1. macOS Preview — no download, no account

Preview has done this since Snow Leopard and most Mac owners never find it, because it is hidden behind an Export dialog rather than a Protect menu.

1. Open the PDF in Preview.
2. File ▸ Export… (not Save As — Export is the one with the options).
3. Give the copy a new name, so the unprotected original survives.
4. Click Permissions.
5. Tick Require Password To Open Document, type the password twice.
6. Apply, then Save.

The dialog also offers an owner password and tick-boxes for printing and copying. Those are a different mechanism and much weaker — see what PDF password protection actually protects. For genuine protection, only the first box matters.

Preview writes AES-128. That is not breakable by anyone you are likely to be worried about; the weak point is always the password you chose, not the cipher.

2. Microsoft Word — when the PDF starts life as a document

If the thing you are protecting is a Word document you are about to turn into a PDF, do both in one step.

• Windows: File ▸ Save As ▸ choose PDF ▸ Options… ▸ tick Encrypt the document with a password.
• Mac: File ▸ Save As ▸ File Format PDF ▸ tick Encrypt with password.

The same option exists in Excel and PowerPoint. It does not exist in Google Docs, which is the first of this guide's two disappointments — see method 7.

3. LibreOffice — free, offline, and the strongest of the desktop options

LibreOffice will open a PDF in Draw and export it again, so you do not need the original document.

1. File ▸ Open, pick the PDF (it opens in LibreOffice Draw).
2. File ▸ Export as ▸ Export as PDF…
3. Open the Security tab, click Set Passwords…
4. Fill in Set open password. Leave the permissions password alone unless you know why you want it.
5. Export.

LibreOffice writes AES-256, the strongest option available in the PDF 2.0 specification, and it does the whole thing on your own machine. For a free tool on Windows, this is the best answer in this list.

4. Adobe Acrobat Pro — if you already pay for it

Tools ▸ Protect ▸ Encrypt ▸ Encrypt with Password, then choose Require a password to open the document. Set Compatibility to Acrobat 10 or later to get AES-256 rather than the older 128-bit modes.

Acrobat is the only desktop tool here that will also remove or change a password on an existing file without re-exporting it, which is worth knowing if you inherit a locked file and know the password.

Everything Acrobat does here, LibreOffice and qpdf also do. Do not subscribe for this alone.

5. qpdf — one command, scriptable, and the one we use

For anyone comfortable at a terminal, qpdf is the cleanest tool in this guide. It is on Homebrew (brew install qpdf), apt (apt install qpdf) and Windows via Chocolatey or a release zip.

``sh qpdf --encrypt "openpassword" "ownerpassword" 256 -- in.pdf out.pdf ``

The first password opens the document, the second controls permissions, 256 selects AES-256, and the bare -- ends the encryption options. In qpdf 11 and later the newer spelling is clearer:

``sh qpdf --encrypt --user-password=open --owner-password=owner --bits=256 -- in.pdf out.pdf ``

Two things people trip over. An empty owner password with 256-bit encryption is refused unless you add --allow-insecure, because an empty owner password makes the restrictions trivially removable. And qpdf never modifies files in place — always name an output file.

To take a password off a file you can open:

``sh qpdf --password="openpassword" --decrypt in.pdf out.pdf ``

6. iPhone and iPad — built into Files

Apple added a lock to the Files app that needs no app and no account.

1. Open Files and tap the PDF to open it.
2. Tap the chevron next to the file name at the top.
3. Choose Lock PDF.
4. Type the password twice and tap Done.

One important limitation: the Files app can lock a PDF but will not unlock or change the password afterwards. If you forget it, you need the original file back. Lock a copy, not your only version.

On Android there is no equivalent built in. Use method 7 or method 8.

7. What does not work — and why

Google Drive and Google Docs cannot password protect a PDF. Drive has no encryption option on export, and File ▸ Download ▸ PDF from Docs produces an unprotected file. Drive's sharing controls restrict who can open the file in Drive; once it is downloaded, that protection is gone. Google's own help pages point you at third-party software for this.

Microsoft Print to PDF cannot either. The virtual printer built into Windows has no security settings at all. Neither does Chrome's Save as PDF.

A password-protected ZIP is not the same thing. It protects the file in transit; the moment anyone extracts it, the PDF inside is naked and can be forwarded to anybody.

Online "protect PDF" tools — Smallpdf, iLovePDF, Adobe's web tools — do work, and for a non-sensitive file they are fine. But read what you are doing: you are uploading an unencrypted document to a third party so that they can encrypt it and send it back. If the document is sensitive enough to deserve a password, it is sensitive enough not to be uploaded in the clear first. Use LibreOffice or qpdf instead; both run entirely on your own machine.

8. Put the password on the link instead

Everything above bakes the password into the file, which means three things at once: you must tell the recipient the password over a second channel, you can never change it, and you will never know whether anybody opened the document.

If the document is something you are sending to a person — a proposal, a portfolio, a report, a price list — the delivery is usually the thing worth protecting.

With PDFLink you upload the PDF, set a password on the link, and send the address. The recipient types the password in the browser and reads the document there. Nothing is downloaded unless you allow it.

What that buys you over an encrypted file:

• Change or remove the password after you have sent the link.
• Retire the link when the proposal is dead, and the document stops existing on the internet.
• See who opened it, when, and how far they read.
• Swap the file for a corrected version without sending anything again — the address and its QR code keep working.
• Ask for an email before the document opens, if you want to know who is reading a forwarded link.
• Set an expiry date, so an old document stops being a live one.

And the honest limitation: this protects the delivery, not the file. Once a reader has downloaded the PDF, it is an ordinary PDF. If what you need is a file that stays encrypted wherever it travels — an archive, a document going to an auditor, anything that must survive being emailed onward — encrypt the file with method 3 or 5, and send that file through a protected link. The two approaches stack.

Choosing a password worth the trouble

Every method above is limited by the same thing: PDF encryption derives its key from your password, so a weak password makes AES-256 exactly as strong as a four-digit PIN. Cracking tools try dictionary words and dates first and will get through most human-chosen passwords in minutes.

Use a passphrase of four or more unrelated words, or a generated string from a password manager. And send it through a different channel from the document — a password in the same email as the attachment protects nothing at all.

Can a password protected PDF be cracked?

If it has an open password and that password is strong, no — AES-128 and AES-256 are not brute-forceable. If the password is a word, a name or a date, yes, quickly. If the file only has an owner password setting permissions (no printing, no copying), then it is not really protected: any number of tools strip those flags in seconds, because the file is not encrypted against the reader in the first place.

How do I password protect a PDF for free?

On a Mac, use Preview (method 1). On Windows or Linux, use LibreOffice (method 3) — it is free, works offline, and writes the strongest encryption of any tool here. On an iPhone, use Files (method 6). Avoid uploading a sensitive document to an online protector just to have it encrypted.

How do I password protect a PDF in Google Drive?

You cannot. Drive and Google Docs have no PDF encryption feature; downloading a Doc as a PDF produces an unprotected file, and Drive's sharing permissions stop applying the moment the file is downloaded. Download the PDF and encrypt it with LibreOffice or Preview, or share it through a password-protected link instead.

What is the difference between a user password and an owner password?

The user password (also called the open password) decrypts the document — without it there is nothing to read. The owner password sets permission flags asking readers not to print or copy, and honouring those flags is voluntary on the reader's part. Only the user password is real security. There is a longer explanation here.

Can I remove a password from a PDF?

Yes, if you know it. qpdf --password="thepassword" --decrypt in.pdf out.pdf does it in one line, and Acrobat Pro does it from Tools ▸ Protect. If you do not know the password and the file has a strong one, there is no legitimate way in — which is the entire point.

Does a password protect a PDF from being forwarded?

No. An encrypted PDF can be forwarded to anyone; they just need the password too, and the person you sent it to can pass that along. If what you want is control over who reads a document after you send it, you want a link you can revoke and an email gate, not an encrypted attachment.