https://www.pbainbridge.co.uk/2019/01/convert-doc-to-pdf-and-move-into-new.html

Convert Doc to PDF and move into a new folder.gs

function convertToPDF() {
  
  // ID of current Google doc
  var docID = '123456789';
  
  // ID of new folder location
  var folderID = '987654321';
  
  // create PDF version of doc *************************************************
  var docFile = DriveApp.getFileById(docID);
  var blobFile = docFile.getAs('application/pdf');
  var pdfVersion = DriveApp.createFile(blobFile);
  
  // get ID of PDF version
  var pdfVersionID = pdfVersion.getId();
  
  // get PDF file
  var pdfFile = DriveApp.getFileById(pdfVersionID);
  
  // get location of where PDF file currently exists (so 'My Drive')
  var parents = pdfFile.getParents();
  
  /* add PDF file to new folder location (so is ignored from above 'parents' 
  and hence will not be removed from this new location) */
  DriveApp.getFolderById(folderID).addFile(pdfVersion);
  
  /* once PDF file has moved, remove it from any other locations so it
  only exists in the new location */
  while (parents.hasNext()) {
    var parent = parents.next();
    parent.removeFile(pdfFile);
  }
  
  // delete the original Google doc file
  docFile.setTrashed(true);
  
  //end of create PDF version of doc ******************************************
  
}