Portable Document Format is a file standard developed by Adobe to allow documents to be distributed electronically while maintaining layout integrity.
PDFs are useful where a large amount of information is to be provided and where reading such material onscreen in unfeasible or inappropriate.
To create PDF documents you will need to purchase the Adobe Acrobat software.
Adobe also provides a web-based version of the software. This allows you to create 3 PDF documents for free. If you live in the U.S. or Canada you can also pay a monthly subscription fee to create all your PDFs online.