Printing a web page might sound like a bad idea. But CSS and browsers are capable of rendering a good looking PDF document ready for any printer. That means you can use every web development technique you want. Without animations, of course.

Sizing

You can specify document size like this:

html, body{
  width: 210mm;
  height: 297mm;
  margin: 0;
}

@page{
  size: A4;
  margin: 0;
}

@media print{
  html, body{
    width: 210mm;
    height: 297mm;
  }
}

I like to get rid of default margins. You should also prefer using cm and mm units over px. This will allow you to fine tune the design.

Colors

By default, browsers try to optimize colors to cut the ink cost of printing. If you want to have pretty colored PDF anyway, then you want to adjust this:

*{
  print-color-adjust: exact;
}

Printing

I use Firefox and results are good. All you need to do is to select Print... in your browser. Print using the system dialog... option allows to enable background colors and images. You can also remove automatic header and footer there.