
https://pandoc.org/MANUAL.html

--data-dir=DIRECTORY
Specify the user data directory to search for pandoc data files. If this option is not specified, the default user data directory will be used. On *nix and macOS systems this will be the pandoc subdirectory of the XDG data directory (by default, $HOME/.local/share, overridable by setting the XDG_DATA_HOME environment variable). If that directory does not exist and $HOME/.pandoc exists, it will be used (for backwards compatibility). On Windows the default user data directory is %APPDATA%\pandoc. You can find the default user data directory on your system by looking at the output of pandoc --version. Data files placed in this directory (for example, reference.odt, reference.docx, epub.css, templates) will override pandoc’s normal defaults. (Note that the user data directory is not created by pandoc, so you will need to create it yourself if you want to make use of it.) 
