grid = new webix.ui({
    view:"datatable",
    columns:[...],
    "export":true
});

<input type="button" value="Get as PDF" style='width:400px;margin:25px;' onclick="grid.exportToPDF();">

{
            container:"testA",
            view:"datatable",
            columns: <?= $json; ?>,

            id: "iddatatable"

            footer:false,
            autoheight:false,
            data:<?= $json_body; ?>,
            scrollAlignY:true,
            export:true,
            resizeColumn:true,
            resizeRow:false,
            dragColumn:true
        }

$$('iddatatable').exportToPDF();