PDF files are a good way to share documents with other people. All of the document formatting, fonts, etc. will retain its original look so that you don't have to worry about how it will look or work on other computers.
Adobe Acrobat has been the industry standard for creating PDFs but there are free alternatives.
PrimoPDF will let you create a PDF from say a Word or any other kind of file.
PriomPDF installs as a printer and you can use it from any program when you click Print. Just select PrimoPDF as a "printer" after clicking Print and your file will be saved as a PDF document.
Want to quickly convert a webpage to PDF? Then check out the following site.