To generate a PDF with Chart.js, you can use a library like jsPDF. First, you need to create a canvas element and render your chart on it using Chart.js. Then, you can convert the canvas to a data URL and create an image object from it. Next, you can create a new jsPDF instance and add the image to the PDF document using the addImage method. Finally, you can save or download the PDF document using the save or output method.