Password-protect a PDF
Set a password and the PDF won't open without it. The file is encrypted with 128-bit AES on your own device; neither the PDF nor the password is sent anywhere.
Updated November 5, 2026 · 2 min read
Choose the PDF to protect
Then set the password that opens it.
Your file never leaves your device. It's encrypted right here in your browser with 128-bit AES. Neither the PDF nor the password is uploaded.
On this page
How to add a password
- 1
Choose the PDF
Pick the file from your device. A PDF that already has a password has to be unlocked first.
- 2
Set the password
Type it twice. Use 4 to 32 characters you can type on any keyboard; a short phrase is easier to remember and harder to guess than one word.
- 3
Add limits if you want them
Tick Block printing or Block copying text. People with the password can still open and read the file.
- 4
Download and test it
Tap Protect and download, then open the new file once to see it ask for the password.
What the password protects
The open password encrypts the file's contents, so without it the pages are unreadable, not just hidden. The printing and copying limits are different: they're instructions that most PDF apps follow, but someone with the password and the right software can get around them. Treat the password as the lock and the limits as a firm request.
Sharing the password safely
- Send the password a different way from the file: text it if you emailed the PDF.
- Keep it out of the file name and the email subject line.
- Save a copy somewhere safe. A lost password can't be recovered by anyone, us included, because we never see it.
Other ways to do it
Word for Windows can encrypt a PDF with a password in the options when you save as PDF. Preview on a Mac can require a password when you export. Paid Adobe Acrobat plans have a Protect tool with more settings.
Protecting a signed contract
A signed agreement usually needs a different kind of protection: proof that nobody changed it. Every PDF signed through SignMaster carries a SHA-256 fingerprint and a certificate of completion, so any edit after signing can be detected. See tamper-evident PDFs.
Questions? Answers.
How strong is the encryption?
It's 128-bit AES, which every common reader opens: Acrobat, Preview, Chrome, Edge and phone viewers. The password's length matters more than the cipher, because short passwords can be guessed.
Can you recover my password if I forget it?
No. The password never leaves your browser, so there's nothing for anyone to recover. Keep a copy before you share the file.
Can I remove a password from a PDF here?
No, this tool only adds protection. To remove a password, open the file with it in a PDF app and save or export a copy without one.
Does it work on a phone?
Yes, in Safari, Chrome or any current browser. The protected file saves to your downloads, ready to attach to an email.