Counting Pages in Google Doc - can't be done BUT if you make it a PDF you can. Here is link: https://stackoverflow.com/questions/36432487/how-to-get-the-number-of-pages-in-google-docs-via-google-script

pagecountWork.gs

function getNumPages() {
  var blob = DocumentApp.getActiveDocument().getAs("application/pdf");
  var data = blob.getDataAsString();
  var pages = parseInt(data.match(/ \/N (\d+) /)[1], 10);
  Logger.log("pages = " + pages);
  return pages; 
}