How to Password Protect a PDF on Windows, Mac and Phones

Here is how to password protect a PDF: save or export it with an open password, so nobody can see the pages without typing it. On a Mac, Preview does this for free; on Windows, Microsoft Word can do it when you save as PDF; on any device, an online tool such as FileKiwi Protect PDF works in the browser. Pick a long password and send it separately from the file.

Open password or permissions password?

PDF protection comes in two layers, and most apps let you set one or both. Decide first what you want to stop.

For bank details, medical letters, ID scans and payslips, you want the open password. Permissions alone keep honest people from printing a draft, nothing more. Readers such as Chrome, Preview and Adobe Acrobat Reader respect them, but other software can ignore them, and unlock tools remove them without any password.

How to password protect a PDF online with FileKiwi

The Protect PDF tool adds an open password in the browser on Windows, Mac, iPhone and Android.

1. Open Protect PDF and add one or more PDFs. Every file you add gets the same password.
2. Type a password of 4 to 64 characters, then type it again to confirm.
3. If you also want to stop printing and copying, turn on Also block printing and copying. It is off by default.
4. Download the result, named like contract-protected.pdf.

The tool uses the standard PDF password protection with a 128 bit key (RC4, PDF security revision 3). Every common reader can open the result with the password: Adobe Acrobat Reader, Chrome, Edge, Firefox, Preview on Mac and the PDF viewers on iPhone and Android.

The PDF is rewritten by Ghostscript on the FileKiwi server. Pages, text, images, links and bookmarks are kept, but fillable form fields may become flat text, so fill in forms first. The password travels with the request over HTTPS and is not stored, so FileKiwi cannot remind you of it later.

A copy of each PDF you add is kept in a private folder on the server for 30 days and then deleted; the protected result is not stored. If a file already has an open password, the tool asks you to remove it first, which our guide on how to remove a password from a PDF explains.

Password protect a PDF on Windows with Microsoft Word

Windows 11 has no built in way to encrypt a PDF. Microsoft Print to PDF creates PDFs but has no password option. If your document starts in Word, though, Word for Windows can encrypt the PDF while it saves it.

1. In Word, choose File, then Save a Copy (or Save As for a new document).
2. Select Browse to open the save window.
3. In the file type list, choose PDF.
4. Click Options.
5. Tick Encrypt the document with a password and click OK.
6. In the Encrypt PDF Document box, type the password twice and click OK.
7. Click Save.

Microsoft lists this option in its guide to saving as PDF in Office apps. Word only encrypts PDFs it creates itself; to protect an existing PDF on Windows, use the browser tool.

Password protect a PDF on a Mac

With Preview

1. Open the PDF in Preview.
2. Choose File, then Export. Give the file a new name if you want to keep the original without a password.
3. Click Permissions.
4. Select Require Password To Open Document, enter a password and type it again.
5. Untick any action you want to block (printing, copying and so on), then enter an Owner Password twice.
6. Click Apply, then Save.

The owner password controls the permission settings. It can be the same as the open password or a different one. To change the settings later, open the file and choose File, then Edit Permissions.

From any Mac app, Microsoft Word included

Word for Mac has no password option in its Save As PDF window. Use the macOS print window instead, which works in Word, Pages, Safari and most other apps.

1. Choose File, then Print.
2. Open the PDF menu at the bottom and choose Save as PDF.
3. Click Security Options and tick the password you need: for opening, copying or printing.
4. Type the password, click OK, then Save.

Password protect a PDF on iPhone and Android

iPhone with iOS 26

iOS 26 includes a Preview app for PDFs, and Apple's guide to locking PDFs in Preview on iPhone describes these steps:

1. Open the PDF in the Preview app.
2. Tap the arrow next to the file name, then tap Lock.
3. Turn on Require Password, enter the same password in the Password and Verify fields, and tap Done.

The lock is applied to the file itself. Apple suggests making a duplicate first if you want to keep a copy without a password. Older iOS versions placed similar options elsewhere, so the menus can differ on an older iPhone.

Android

Android has no standard built in way to encrypt a PDF, and the PDF apps that come with phones differ by brand. Open Protect PDF in Chrome, choose the file from Downloads or Google Drive, set the password and save the result.

How strong is PDF password protection?

The open password is real encryption: without it, the pages are unreadable data. In practice, the weak point is almost always the password itself. Programs that attack PDFs try huge numbers of guesses, so a short word or a birth date falls quickly, while a long random phrase does not.

• Use at least 12 characters. Four random words, such as river lamp orange cactus, are easy to type and hard to guess.
• Avoid personal facts that appear on the document, such as names, dates of birth or account numbers.
• Use a new password per file or per recipient, so one leaked password does not open everything.

RC4 with a 128 bit key, which FileKiwi and many other tools use, is an older cipher than the AES encryption that some newer PDF software offers. For a contract or a payslip sent by email it is enough when the password is long. For highly sensitive material, also store and send the file through a channel you trust.

Remember what the password does not cover. Once the right person opens the file, they can save, forward or print it like any other PDF, unless you also set restrictions. Those restrictions only hold in apps that choose to respect them, so treat them as a reminder, not a lock.

Sharing a protected PDF the right way

A password sent in the same email as the file protects very little. Anyone who gets the email gets both.

• Send the PDF by email and the password by text message or a phone call.
• Agree on a password once with people you send files to regularly, and never write it in the subject line.
• Do your edits first. Merging, compressing or adding page numbers usually needs an unprotected file, so finish with Compress PDF or other tools, and protect the PDF as the last step.

If the PDF is a form you filled in, consider Flatten PDF before protecting it. Flattening turns the typed answers into fixed page content, so the person who opens the file sees exactly what you entered and cannot change it by accident.

Also test the result before you send it. Open the protected file on your phone, type the password and check that every page is there.

Which method to pick

• Writing the document in Word on Windows: encrypt it while saving as PDF.
• On a Mac: Preview Export with Permissions, or Save as PDF with Security Options from any app.
• On iPhone with iOS 26: Lock in the Preview app.
• Existing PDF on Windows or Android, or several files at once: Protect PDF in the browser.

Whatever you use, keep the password somewhere safe, such as a password manager. Nobody, FileKiwi included, can recover a forgotten open password for you.

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