code: public void readAcroForm(PdfDictionary root) {
          if (root == null)
              return;
          hashMap = root.hashMap;
          pushAttrib(root);
          PdfArray fieldlist = (PdfArray)PdfReader.getPdfObjectRelease(root.get(PdfName.FIELDS));
          iterateFields(fieldlist, null, null);
      }
docs: Read, and comprehend the acroform
  @param root the document root