The prebuilt files include `web/pdf_viewer.js` with some viewer APIs. Those are missing from type declarations.
console.log();
  console.log("### Building default preferences");
  const bundleDefines = builder.merge(defines, {
    LIB: true,
    SKIP_BABEL: false,
    BUNDLE_VERSION: 0, 
    BUNDLE_BUILD: 0, 
    TESTING: defines.TESTING || process.env.TESTING === "true",
  });
  const inputStream = merge([
    gulp.src(["web/{app_options,viewer_compatibility}.js"], {
      base: ".",
    }),
  ]);
  return buildLibHelper(
    bundleDefines,
    inputStream,
    DEFAULT_PREFERENCES_DIR + dir
  );
}
function getDefaultPreferences(dir) {