Protect PDF

It adds a password and AES-256 encryption to a PDF. Encryption scrambles the file contents using a key derived from your password, so the document cannot be read until the correct password is entered. You can set a viewing password on its own or add an owner password with permission controls for printing, modifying, and copying.

The user password is required to open and view the file, since the decryption key depends on it. The owner password governs editing rights and permission flags written into the encrypted file. With an owner password set, viewers can read the document using the user password but cannot modify, print, or copy it unless those permissions are allowed.

No. All encryption runs in your browser, so the PDF and the password stay on your device. The key is derived locally and applied to the file before you download it. Nothing about the password or the document contents is transmitted, which is why you should keep a copy of the password yourself.

The tool uses AES-256, a 256-bit block cipher widely relied on for document protection. The password you enter feeds into the key that scrambles the file, so a longer, less predictable password produces stronger practical protection. AES-256 is the same class of encryption used for many banking and government documents.

Yes. Expand Advanced Options, set an owner password, and clear the Allow Printing, Allow Modifying, or Allow Copying checkboxes as needed. These permission flags are stored in the encrypted file and honored by compliant PDF readers, which check them before letting a viewer print, edit, or select and copy text.

Because the file is encrypted with a key tied to your password, there is no backdoor to recover it. If you lose the user password, the contents cannot be read. Store the password somewhere safe before you share the file. If you still have access to an unprotected copy, you can encrypt it again with a new password.

Use the Remove Password Protection tool. You supply the current password, and it decrypts the file and saves an open copy. This is the reverse of encryption: instead of scrambling the bytes, it uses your password to unlock them and rewrite the document without protection.

No. The pages, text, and images stay exactly as they were. Encryption wraps the existing content in a protective layer rather than editing it. When the correct password decrypts the file, the reader displays the original document unchanged. The only difference a viewer notices is the password prompt before the file opens.

Yes, and the distinction matters. Password protection encrypts the whole file, so an authorized viewer sees everything once they unlock it. Redaction permanently deletes specific content from the document, so nobody sees it regardless of passwords. Use encryption to control access and redaction to erase sensitive details entirely.

The tool accepts a single PDF file per run. If you have several documents, encrypt them one at a time, or combine related files first with Merge PDF and then apply one password to the joined document. Each file keeps its own password unless you merge them into one.

The user password is enforced by the encryption itself, so no reader can open the file without it. Permission flags such as no printing or no copying rely on the reader honoring them. Most mainstream readers do, but the open-password layer is the stronger control because it locks the file rather than trusting the viewer's software.

Because the work runs in your browser, the practical limit depends on your device memory rather than a fixed server cap. Very large files take longer to encrypt and use more memory. If a file is unwieldy, shrink it first with Compress PDF , then apply the password to the smaller result.