PDF stands for Portable Document Format Invented by Adobe, PDF is now a standardized design maintained by the International Organization for Standardization (ISO). Generally PDFs can contain links and buttons, form fields, audio, video, and business logic. They can also be signed electronically and are easily viewed using free Acrobat Reader DC software which can also be an editable. Each PDF file summarizes a complete description of a fixed-layout flat document, including the text, fonts, graphics, and other information needed to display it. PDF was developed as a way to share computer documents, including text formatting and inline images which can be read, navigate, print and downloaded easily. PDF used to present documents in a manner independent of application software, hardware, and operating systems.

A full-text database is assemble of documents or other information in the form of a database in which the complete text of each referenced document is available for online viewing, printing, or downloading. In addition to text documents, images are often included, such as graphs, maps, photos, and diagrams. A full-text database is searchable by keyword, phrase, or both. When a document appears as a PDF file, it is usually a scanned hardcopy of the original article, chapter, or book. Full-text databases are ideally suited to online courses of study, where the reader remains at their place and obtain materials by downloading them from online. Full-text databases are also used by the U.S Internal Revenue Service and most state departments of revenue are good examples.