FD is a support file for documents written in LaTeX language. FD files contain font declarations for text documents. FD files stores data in text format and contains commands used b LaTeX for setting fonts and their properties.

Modifications made to FD file will be reflected in all files that use it. Working with FD files requires some level of proficiency in LaTeX. Language. FD files can be edited using any text editor, but their usage is strictly limited to LaTeX enviroment.