PDF means "Portable Document Format". It stores a document's content and layout in a way that means that one program on your computer can read PDFs produced by another computer, no matter what program made the PDF.
One program on your computer? Yes... all you need is Acrobat Reader, or as it's becoming known Adobe Reader.
Acrobat Reader is a free program for home computers. Download it from Adobe's website at www.adobe.com
Each PDF has the content, layout and all the fonts inside so you see it just as we did when we made it. To print the free music, order forms & posters on hago.org.uk, you don't need the software we used, you just need Reader and a PC or Mac.