Load your collection. Select Print from your browser (not by clicking on the printer icon on the page). One of the selection boxes in the dialog, will have the name of your printer in it. But instead, you want to change it to "Print to PDF." Then when you click to proceed, it will ask you where you want to save it. But you will need to do it for each page. So if your collection is 20 pages long, you will have to do it 20 times. Also, remember the next time you want to Print from your browser like normal, you will have to switch the selection box back to the name of your printer.