doPDF is a free program for creating PDFs. The software is quite simple, but it does the job, no more no less. If you are looking for a free application to make PDFs quickly, this is as good as it gets. Its native print option allows you to produce PDFs from any program. When you choose the Print option, you will see the doPDF option along with the rest.
The most common conversion is .doc to PDF, but there is support for .txt, HTML, .docx and many others. You can change the size of the paper, the quality settings and the orientation. For many users though the standard settings will be fine.