If you find yourself in a situation to create PDF documents quickly and free of charge, I will recommend PDFCreator.
PDFCreator allows easy creation of PDFs from any Windows application. Use it like a printer, in Word, Internet Explorer (great to print bank statements, travel bookings) or even Visual Studio (if you need to print your source code). It even allows you to set security and file settings! Great stuff, essential software for every PC.
Remember always RTFM or put it politely: read the readme file to select the appropriate version to download :)