Don't get me wrong, it's great that @calixteman wanted to implement that — JS should definitely be supported! I don't want to come off as rude or attacking.

For starters, JS reference specified in the [commit comment](https://github.com/mozilla/pdf.js/commit/8de98079ca05f8f7001ee077771055a57dc0e948) is outdated. It's version 8.1 from 2007… We're more than decade past that now. We should be implementing [Acrobat DC SDK](https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/AcrobatDC_js_api_reference.pdf) ([here](https://help.adobe.com/en_US/acrobat/acrobat_dc_sdk/2015/HTMLHelp/#t=Acro12_MasterBook%2FJS_API_AcroJS%2FJavaScript_API.htm) in a nice HTML version).

Other than that, the Doc object now is only implemented with `info` property with standard fields (`Title`, `Author`, `Subject`, `Keywords`, `Creator`, `Producer`, `CreationDate`, `ModDate` and `Trapped`, case insensitive). But [according to the spec](https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/AcrobatDC_js_api_reference.pdf#page=243) (even [in that old version](https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/js_api_reference.pdf#page=243)), this object can contain other, non-standard properties, that can be set both in Acrobat interface and in JS (which are case-sensitive then).

Acrobat 9.0 introduced another field to that property, `Authors`, containing semicolon-delimited list of authors.

There are probably other problems with that code due to the outdated spec @calixteman was apparently working on.
const { path, value } = xfa;
    if (!path) {
      continue;
    }
    const node = xml.documentElement.searchNode(parseXFAPath(path), 0);
    if (node) {
      node.childNodes = [new SimpleDOMNode("#text", value)];
    } else {
      warn(`Node not found for path: ${path}`);
    }
  }
  const buffer = [];
  xml.documentElement.dump(buffer);
  let updatedXml = buffer.join("");
  const encrypt = xref.encrypt;
  if (encrypt) {
    const transform = encrypt.createCipherTransform(
      datasetsRef.num,
      datasetsRef.gen
    );
    updatedXml = transform.encryptString(updatedXml);
  }
  const data =
    `${datasetsRef.num} ${datasetsRef.gen} obj\n` +
    `<< /Type /EmbeddedFile /Length ${updatedXml.length}>>\nstream\n` +
    updatedXml +
    "\nendstream\nendobj\n";
  newRefs.push({ ref: datasetsRef, data });
}
function incrementalUpdate({