Calling all Articulate JavaScript buffs

In your code:

  const { PDFDocument } = PDFLib;
  const formUrl = 'PDFen.pdf';
  
  const formPdfBytes = await fetch(formUrl).then (res => res.arrayBuffer());
  const pdfDoc = await PDFDocument.load(formPdfBytes);
  const form = pdfDoc.getForm();
  alert ("Helb");

You are attempting to open an existing pdf form template file "PDFen.pdf" and read the contents into a byte array. You are then using pdf-lib routines to read the pdf template from the byte array and create a new pdf form "form".

Your error message " Failed to load resource: net::ERR_FILE_NOT_FOUND               PDFen.pdf:1" indicates that your JavaScript code cannot find the pdf form template file.