The main ES6 file is src/athenapdf.js. Plugin-related files are prefixed with plugin_.
For local development, start by checking out this repository, and then install the dependencies using npm install.
To test your changes, run ./bin/athenapdf <input_path> [output_path]. Ensure the aforementioned file has the necessary permissions to be executed (i.e. chmod +x ./bin/athenapdf).
You can use athenapdf globally, and test your changes live by running npm link in the athenapdf/cli directory.