Sending a contract or payslip by email and want only the person with the password to see it? Learn how to protect a PDF in your browser, choose a password and use AES-128 encryption.
Only someone who knows the password can open a password-protected PDF. Its content remains inaccessible to everyone else.
This is useful for a contract or quotation travelling through several email servers, a medical report intended for one relative, individual payslips or a document stored in a shared cloud folder. Adobe Reader can open an encrypted file but cannot set a new password; that requires paid Acrobat or another tool. This guide shows you how to protect a PDF in your browser, choose and share the password safely, understand AES-128 encryption and check the file before sending it.
How to password-protect a PDF in your browser
Open Password Protect PDF and follow four steps.
- Choose the PDF. Click Choose PDF or drag the file into the marked area. It loads only into the browser tab.
- Enter a password. Type at least six characters in New Password and repeat it. If the entries differ, the tool explains what to correct and does not begin encryption.
- Press Password Protect PDF. The content is encrypted on your device without uploading the file or waiting for a server.
- Check and download. The tool verifies that opening without the password fails, opening with the correct password succeeds and every page matches the original. Download PDF appears only after these checks.
The protected copy is saved with a -protected suffix. Your unencrypted original remains untouched on disk; they are two separate files.
Free tool, right in your browser
Password protect PDF
Set a password for opening the PDF and apply AES-128 encryption directly in your browser. The file never leaves your device.
How to choose and share the password
The minimum is six characters, but a longer password is sensible for documents sent outside your organisation. Strength depends mainly on length and unpredictability, not on replacing a few letters with digits. Several unrelated random words are also easier to remember than a short jumble. See How to create a strong password and use the Password Generator if needed.
Do not send the password in the same email as the file. Anyone who gains access to that message would receive both. Use another channel, such as a phone message or call. Save the password in a password manager under the document or recipient's name, and never reuse a login password. Once you share it, you cannot take it back.
If a recipient loses the password, create another protected copy from the unencrypted original with a new password. For a batch such as payslips, use a different password for each person. One password for the whole batch would let any recipient open a colleague's file if they obtained it.
What AES-128 encryption means in practice
The file is saved as PDF 1.7 and encrypted with AES-128. Protection covers page text, images, fonts and information such as title and author. Only the technical file structure, including its header and encryption details, remains readable.
No reader or browser can display the content without the correct password. This is genuine encryption, not a setting that can simply be switched off. The password itself is not stored in the file. The PDF contains a derived value used to verify the entered password, from which the original password cannot be read back.
The tool neither recovers nor guesses forgotten passwords. Keep the unencrypted original on your disk and protect only the copy sent to the recipient.
Open passwords and printing or copying restrictions
PDF supports two kinds of protection, but this tool sets only one. It uses one password as both the user and owner password; the document does not have two separate passwords. All permissions remain enabled. Anyone who knows the password can read, print, copy and edit the document.
You cannot use this tool to create a PDF that opens for everyone but prevents printing or copying. How to unlock a PDF explains the difference and why permission restrictions alone are not dependable security.
What else to check before sending the PDF
Document properties may contain the author's name, title, the program that created it, and creation and modification dates. These travel with the file. A recipient might see the colleague who prepared a quotation or an internal project name.
Use Remove PDF Metadata before encryption. The order matters because the metadata tool rejects encrypted input. Also remove pages that do not belong in the delivery, such as an internal calculation or notes, with Delete PDF Pages, then protect the finished document.
Free tool, right in your browser
Remove PDF metadata
View and remove the author, title, software and dates from a PDF before sending it. The file never leaves your device.
Password-protecting PDF/A and already protected files
The tool rejects two types of file for good reasons.
PDF/A files are intended for long-term archiving. Encryption would make them non-compliant, so the tool reports that password protection would violate the archival format. A document cannot remain PDF/A and be encrypted.
Already protected files must first be passed through Unlock PDF. Enter the document-open password when one is required; if the file merely limits printing or copying, leave the field empty. Then protect the unencrypted copy with a new password. The file never carries two layers of encryption.
Frequently asked questions
Can I password-protect a PDF in Adobe Reader?
No. The free Reader can open protected PDFs but cannot add encryption; that feature belongs to paid Acrobat. Without Acrobat, use Password Protect PDF in your browser without installation or registration.
How can I password-protect a PDF for free without software?
Open Password Protect PDF, choose the file, enter the new password twice and start encryption. Processing runs in the browser tab, and you save the protected copy with Download PDF. It works on computers and mobile devices.
Will a protected PDF open on a phone and in every browser?
The recipient needs a reader that supports AES-128 password encryption. Common desktop readers, browsers and mobile apps do. After the password is entered, all permissions remain enabled; which print and copy controls appear depends on the application.
What if I forget the password?
The tool cannot recover or guess it. If you retained the unencrypted original, protect it again with a new password and resend the copy. Otherwise, search your password manager or notes.
Is the password or file sent anywhere?
No. Both remain in the browser tab and encryption happens on your device. Neither is sent to a server, so no remote copy is created that later needs deleting.
Can I change or remove the password later?
Yes, if you know it. Unlock PDF creates an unprotected copy, which you can use directly or protect with a new password. The existing protected file remains unchanged on disk, so you can keep both versions.
