Regularly through this website, there are opportunities for you to download documents - which are in "PDF" format.
"PDF" stands for "Portable Document Format". PDF/pdf is a format that allows a document created in any word processor or other software to be viewed electronically without the reader having the original software, and with the identical layout/format as the original.
The most commonly used software for reading pdf is Adobe Acrobat Reader. If you do not currently have this it can be readily downloaded for FREE by clicking on the icon below: