PDF not rendering in Node.js

Question

I am trying to generate a PDF file in some method and then display it in browser. So far, what I have is this:

 nightmare 
    .goto(url) 
    .wait('body')
    .evaluate( ()=>document.querySelector('body').innerHTML) 
    .end() 
    .then((response) => { 
        return getJSONData(response);
    })
    .then((data) => {
        return limiter.schedule(() => processJSONData(data));
    })
    .then((pages) => {
        createFile(res, url, pages);  
    })
    .catch(err => { 
        console.log(err); 

The createFile() method creates the PDF file :

function createFile(res, url, data){
    var pdfdoc = new PDFDocument;

    var fileName = "My_File.pdf";
    pdfdoc.pipe(fs.createWriteStream(fileName));
    var pagelist = data.toString().split(",");
    // Add a new page and create the PDF by adding each image per page
    const pages = pagelist.map(page => {
        pdfdoc.addPage();
        pdfdoc.image(page, {scale:0.45, align:'center', valign:'center'}); 
    });
    // Once all pages are finished, mark the end of document, log and return the filename
    Promise.all(pages).then(() => {
        pdfdoc.end();
    }).then( () => {
        console.log("PDF file created : "+fileName);
        renderPDF(res, fileName);
    })
}

I have the method renderPDF() as follows :

function renderPDF(response, mangaName) {
    var dest = path.resolve(mangaName);
    console.log("Rendering PDF file "+dest);
    console.log("Response object content follows.");
    response.sendFile(dest);
}

I do not understand exactly what I am doing wrong here. I even tried this but it pops out the file with 0 bytes content. How can I fix this?