If you've never heard of a program like PDFCreator before, you might find it a tad odd, but trust me, virtual printer software is DEFINITELY something you want to have on your computer. Why? Well, for starters, if you've ever wanted to save something without having to use paper (say, a receipt while online shopping), you can just print it to a PDF instead. Also, PDFCreator is great if you want to "convert" anything that can be printed into the PDF format.
When you go to print something, all you have to do is select "PDF Creator" from the list instead of your hardware printer. Then, after whatever program is printing is done, it will hand the file over to PDFCreator, and you'll be prompted for a filename. Name it, click save, and you're done. It's that easy. It also has a ton of options like the ability to integrate into the shell, or make it auto-save with the date and time as a filename.
One surprising thing about PDFCreator is that it is not limited only to PDF files. Although that is the default, it can also "print" to PNG, JPG, BMP, PSD, TIFF, and several more. Another surprising thing is that PDFCreator does not just take a "snapshot" of the thing being printed. If you use a PDF reader, you probably know that on some PDFs, you have the ability to search for text, because the text is actually in the PDF. When PDFCreator prints a file, it doesn't just "flatten" it to a picture, it includes the text. So if you print a word document, you can then search through the text in the PDF you've printed. I don't use PDFs that much, but I thought that was pretty nifty.
Virtual Printers are one type of software I can't live without. The uses are endless. You can use it for anything from just creating a PDF of a letter to your cousin to taking a section of a multipage PDF by "printing" that section with PDFCreator. The only downsides are (1) it's like installing hardware so there are drivers, (2) it's not portable, since it's like installing a real printer, and (3) it's not a lite install. PDFCreator takes at least 21mb, probably a bit more including drivers. But if you can spare the space, it's totally worth it. Plus, it's even open source.