There are a number of ways to create a pdf file by using open source software. For example, openoffice can export their document files into PDF. But How's about others file type? For example, how can I export a web page into PDF?
I found the best way is getting a PDF Printer driver. I just need to open the file and print it into a PDF Printer. Then it will "print" into a pdf file. I am using PDFCreator to do this task. It is free and opensource.