Add Password Protection to PDFs Password protect PDF.

The tool uses client-side JavaScript with React to handle file uploads and password protection. When a PDF file is dropped into the FileDropzone component, it triggers the handleFile function, which loads the file using the arrayBuffer method and then utilizes the pdf-lib library to extract the page count. The evaluateStrength function assesses the complexity of the user-provided password based on factors such as length, letter case, numbers, and special characters, returning a score between 1 and 4. This score is then used to display a color-coded strength indicator, helping users choose a secure password.

The process function applies password encryption to the PDF document by creating an /Encrypt dictionary compatible with PDF 1.7 standards. It uses the crypto.subtle.digest method to generate a SHA-256 hash of the user-provided password and then constructs the encryptDict object, which includes properties such as Filter, V, R, Length, O, U, and P. The pdf-lib library is used to register this dictionary with the document's trailerInfo, effectively applying the password protection. Upon successful encryption, a Blob object containing the protected PDF is created, and its URL is generated using the URL.createObjectURL method.

The tool also leverages React's useMemo hook to memoize the password strength evaluation, ensuring that it only recalculates when the password changes. The Clipboard API is not explicitly used in this code snippet, but it could be utilized to implement features like copying the protected PDF link to the clipboard. A responsive UI is implemented using CSS classes and a grid-based layout, allowing for a seamless user experience across various devices and screen sizes. By operating entirely on the client-side, the tool minimizes the risk of data exposure during transmission, ensuring that sensitive information remains secure throughout the password protection process.