Protect PDF

Password-protecting a PDF prevents unauthorised users from opening, printing, or modifying the document. This is essential for sharing confidential contracts, financial documents, personal identification, or any file that should only be accessible to specific recipients.

PDF encryption works by applying a symmetric encryption algorithm to the file's content. The password is used to derive the encryption key. Any compliant PDF viewer — including Adobe Reader, Preview on macOS, and browser-based viewers — will prompt for the password before displaying the content.

Two levels of password protection are available in the PDF standard: an "open" password that prevents the document from being opened at all, and a "permissions" password that restricts specific operations such as printing, copying text, or making changes. Both can be set independently.

Encrypted PDFs are slightly larger than their unencrypted originals due to the overhead of the encryption metadata. For very sensitive documents, consider compressing the PDF before encrypting it to keep the file size manageable.