Software that allows documents to be viewed on computers that do not have the original application that created them. The software comes in two parts. The first part converts the document from its original format into the exchange format for distribution. The second part is a free viewer program that displays the files. Adobe's Acrobat and PDF format are the de facto standard for document exchange (see PDF). Fonts Are Included Unlike file viewers that rely on the fonts installed in the computer to display the fonts accurately, document exchange systems carry the original fonts within the file format to the viewing machine. The fonts are only used for displaying the document and not for general use by the system. See also document imaging and document management system.