PDF.JS下载行为

I was wondering how the pdf.js library handles the download of a pdf page.

If I execute this code:

var test_pdf = "documents/pdf";
    PDFJS.getDocument(test_pdf).then(function(pdf) {
      // Using promise to fetch the page
     pdf.getPage(1).then(function(page) {
     var scale = 1;
     var viewport = page.getViewport(scale);
     var realwidth = viewport.width;
     // Scale all documents to a width of 520px
     var newscale = 520/realwidth;
     var viewport = page.getViewport(newscale); 

     //
     // Prepare canvas using PDF page dimensions
     //
     var canvas = document.getElementById('the-canvas{{slide.page}}');
     var context = canvas.getContext('2d');
     canvas.height = viewport.height;
            canvas.width = viewport.width;

     //
     // Render PDF page into canvas context
     //
     var renderContext = {
      canvasContext: context,
      viewport: viewport
     };
     page.render(renderContext);
 });

So here I only display the first page of the PDF but I think the client downloads the whole pdf right?

If this is right, does anybody maybe if it is possible to only download a given page off the pdf file?

What about idea to split pages from pdf document in several files (e.g. by using PDFtk) and later use/load these pages?