Creating a pdf
If you want your reader to be able to download a file, try to avoid Word or similar files, readers may find difficulty opening them or printing them, better to let them download a PDF.
PDFs cannot be accidently altered and you can be sure they will be able to be opened by pretty well anyone.
You don't need to purchase a PDF writer, there are plenty of free software programmes on the web. Some systems work on-line such as pdfonline.com while others such as dopdf.com can be downloaded to your computer and will create pdfs for you.