Not able to see PDF button in jQuery datatable

Question

I can see CSV button and I'm able to download CSV, but I'm not able to see PDF button, can anyone help me with this?

extend: 'pdfHtml5',
text: 'PDF',
className: 'btn-sm invisible buttons-pdf',
exportOptions: { columns: ':visible' ,stripNewlines: false, trim : false},
title: this.criteria.get('name'),
orientation: 'landscape',
footer: true : false,
customize: function (doc) {
    console.log($colCount);
    console.log(doc);
    let colCount = $colCount;
    doc.styles.tableHeader.fontSize = 12;
    doc.defaultStyle.fontSize = 11;
    doc.styles.tableBodyEven.alignment = 'center';
    doc.styles.tableBodyOdd.alignment = 'center';
    doc.styles.tableFooter = {
        alignment: 'center',
        fillColor:"#2d4154",
        bold: true,
        fontSize: 12,
        color: "white"
    }
    doc.styles.tableBodyOdd.noWrap = true;
    doc.styles.tableBodyOdd.fillColor = '#f3f3f3';
    console.log(doc.content[1].table.body[($rowCount)+1]);
    _.each(doc.content[1].table.body[($rowCount)+1], function(col, key) {
        if(col.text != "") {
            var text  = col.text.split(/\r\n|\r|\n/g);
            col.text = text[1];
        }
    });

    for (i = 0; i <= $rowCount; i++) {
        doc.content[1].table.body[i][0].alignment = 'left';
    };

    var colWidth = [];
    var width;
    
    for (i = 0; i < colCount; i++) {
        width = 100 / colCount;
        colWidth.push(width + '%');
    }

    doc.content[1].table.widths = colWidth;
}

Do I need to import something while extending to pdfHtml5? Am I missing something?