Adding a password to a PDF prevents anyone without the password from opening it. This matters for contracts, financial documents, HR files, personal records, and anything else you share digitally that should not be accessible to just anyone who finds the file.
How you password protect a PDF depends entirely on what device you are using. The steps are different on Mac, iPhone, and Windows — and on Windows in particular, there is no built-in option at all. Here is how to do it on each.
How to password protect a PDF online (any device)
The fastest method on any device — no software needed:
- Open Filero's free Protect PDF tool.
- Upload your PDF.
- Enter a password.
- Download the password-protected PDF.
Works on Mac, Windows, iPhone, and Android. No account, no sign-up. The encryption used is AES-128, which is the same standard used by most PDF readers and Acrobat.
How to password protect a PDF on Mac
Mac has a built-in method through Preview — no software needed:
- Open the PDF in Preview.
- Go to File > Export as PDF.
- Click the "Show Details" button in the save dialog.
- Check "Encrypt" and enter your password.
- Click Save.
The saved PDF will require the password to open in any PDF reader. This is the easiest method for Mac users because it requires nothing extra.
How to password protect a PDF on iPhone
iOS does not have a native way to add passwords to PDFs. Your best options:
Option 1 — Use Filero in Safari: Open Safari, go to filero.app/tools/protect-pdf, upload the PDF from your Files app, set a password, and download the protected file. Takes about 30 seconds.
Option 2 — Use the Files app with a supported cloud:If you store PDFs in iCloud Drive, you can lock them using the Files app (long press the file > Lock). This adds a Face ID/Touch ID lock rather than a password — useful for protecting files on your own device, but the lock does not travel with the file when you share it.
For a password that someone else will need to enter when you share the file, the Filero web tool is the most reliable option on iPhone.
How to password protect a PDF on Windows
Windows has no built-in PDF password tool. Your options:
Option 1 — Use Filero online: The fastest option. Open Chrome or Edge, go to filero.app/tools/protect-pdf, upload the file, set a password, download. Done in under a minute with no software to install.
Option 2 — Microsoft Word (if you have Office):Open the PDF in Word (it will convert it to an editable document). Go to File > Export > Create PDF/XPS. In the Options dialog, check "Encrypt the document with a password". Set the password and save. Note: opening a PDF in Word re-flows the layout which can alter formatting — best used if you were already editing the document.
Option 3 — Adobe Acrobat: The most capable option with full control over permissions (printing, editing, copying). Requires a paid subscription.
Frequently asked questions
What is the difference between a document open password and a permissions password?
An open password (also called a user password) prevents anyone from opening the file without entering it. A permissions password (also called an owner password) allows the file to open but restricts what the reader can do — printing, copying text, or editing. Filero's Protect PDF tool sets an open password. For permissions control, Adobe Acrobat is needed.
Can I remove the password later?
Yes — use Filero's Unlock PDF tool. You will need to enter the current password to remove it.
How strong is the encryption?
PDF passwords use AES encryption. A strong, unique password (12+ characters with mixed case and numbers) is effectively unbreakable by brute force. A short or common password can be cracked with freely available tools. The strength of the protection depends entirely on the strength of the password you choose.
Ready to try it?
Use Filero's free Protect PDF tool. No account needed, works on any device.
Open Protect PDF