This toolwill only work for files that you UPLOAD to Google Drive and uses the following permissions to share: "Public on the web" or "Anyone with the link.
This tool will not work for Google Documents (Documents, Spreadsheets, Presentations, etc.) that created inside Google Drive. If you want to create a direct link for Google Documents (Documents, Spreadsheets, Presentations, etc.) that created inside Google Drive, first download them to your computer then upload that file back on to Google Drive.