(Assuming you have the Google Chrome browser installed already, I mean.)
Open any web page inside Google Chrome, press Ctrl+P (or Cmd+P if you are on a Mac) to open the Print dialog and change the destination printer to “Save as PDF.” Hit the Print button and the current web page will instantly download as a PDF document. Simple!
For me, the Print button changed to a Save button, but it did in fact work.
One more thing. You can also use Chrome’s PDF engine to convert your local image files, text files and any local HTML web pages to PDFs – if you an open a file in Chrome, it can convert the file to PDF.