This format is called Portable Document Format (or PDF for short), and was developed by Adobe Systems. The software used to read and print such files is called Adobe Acrobat Reader, and is available to download for free from Adobe Systems.

If your browser displays these PDF files as text, try holding down the Option key while clicking on the download link (Mac) or Right-clicking on the link and choosing Save Target/Link As...(Windows). This should force your browser to save the file to disk.