   * Clicking on an icon will show the PDF preview on the right side.
         * @param {Event} event - The event triggered by file selection.
         */
        function previewFiles(event) {
            const files = event.target.files;
            const fileListDiv = document.getElementById("file-list");
            const pdfPreviewContainer = document.getElementById("pdf-preview-container");
            const pdfPreview = document.getElementById("pdf-preview");

            fileListDiv.innerHTML = ""; 