Joomla user configuration directory
Profiles live in media/plg_system_wtpdfjs-config/, beside the supplied media/plg_system_wtpdfjs/ directory. Installation creates default.json containing {} if it is absent. Existing files are not overwritten. Create named profiles such as catalog.json and mobile.json yourself.
Plugin updates and uninstallation do not remove the user directory. Include it in site backups. If creation fails, the installer warns you: check permissions and create it manually. Paths are relative to the Joomla root.
JSON is available over HTTP. Store public UI settings only, without passwords, API keys or private tokens. The server must return HTTP 200 JSON, without redirects, login forms or HTML errors.