What's the difference between user password and owner password?

The User password (sometimes called the "open password") gates whether the PDF can be viewed at all — without it, the file is just encrypted bytes. The Owner password (sometimes called the "permissions password") gates editing actions: with the user password, a reader can open the file, but they're still blocked from printing, copying text, modifying pages, or filling forms unless those permissions are granted. The owner password lets the holder remove or change those restrictions. Most use cases only need the user password; add the owner password when you specifically want to allow viewing but block other actions.

Are my files private when I encrypt them here?

Yes — Protect runs entirely in your browser via pdf-lib. Your PDF and your password are processed locally; the encrypted output is generated client-side and downloaded directly to your device. Nothing crosses the network, so even contracts, payslips, and bank statements can be encrypted through this flow without leaving your computer. PDFly does not store the password — if you lose it, the file becomes unreadable.

How strong is the encryption?

PDFly uses 256-bit AES encryption by default — the same standard used by banks and most government systems. With a strong, randomly-generated password (12+ characters mixing letters, digits, and symbols), brute-forcing the file is computationally infeasible with current hardware. The advanced options also let you choose 128-bit AES for compatibility with older PDF readers (PDF 1.6 / Acrobat 7+). The weakest link is almost always the password itself: a guessable password (a name, a date, a dictionary word) defeats even the strongest cipher.

How to password-protect a PDF

PDFs that travel — contracts to clients, payslips to employees, exam papers to graders — often need to be readable only by a specific person. A password makes that explicit: even if the PDF is forwarded, dropped on Slack, or attached to the wrong email thread, it stays opaque without the password.

PDFly's Protect tool offers two layers. The **User password** (required) gates opening: no password, no view. The **Owner password** (optional) gates editing — pick what readers can do (print, copy text, fill forms, add comments) and what stays locked. Both are 256-bit AES encrypted by default; nothing leaves your browser.

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Step 1 — Open the Protect tool
Open the Protect tool. The upload screen titled "Password Protect PDF Files" is where you drop the PDF you want to lock.
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Step 2 — Upload your PDF
Click "Select PDF files" and pick the PDF you want to protect — or drop it onto the page. The password fields appear in the sidebar after upload.
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Step 3 — Set the passwords
In the sidebar, type a password into the "User Password (Required)" field — this is what readers will need to open the PDF. Optionally, set an "Owner Password (Optional)" too: this lets you keep the PDF readable for everyone but lock down which actions (printing, copying, editing) require the owner password to perform.
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Step 4 — Protect and download
Click "Protect File" to encrypt the PDF and start the download. Save the password somewhere safe — without it the file becomes unreadable, and PDFly never stores it. Send the protected PDF and the password through different channels (e.g., email the file, text the password) so a single intercepted message doesn't expose both.