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specified in the [commit comment](https://github.com/mozilla/pdf.js/commit/8de98079ca05f8f7001ee077771055a57dc0e948) is outdated.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There are probably other problems with that code due to the outdated spec @calixteman was apparently working on.
newXref.set("W", sizes);
  newXref.set("Length", tableLength);
  buffer.push(`${refForXrefTable.num} ${refForXrefTable.gen} obj\n`);
  writeDict(newXref, buffer, null);
  buffer.push(" stream\n");
  const bufferLen = buffer.reduce((a, str) => a + str.length, 0);
  const footer = `\nendstream\nendobj\nstartxref\n${baseOffset}\n%%EOF\n`;
  const array = new Uint8Array(
    originalData.length + bufferLen + tableLength + footer.length
  );
  
  array.set(originalData);
  let offset = originalData.length;
  
  for (const str of buffer) {
    writeString(str, offset, array);
    offset += str.length;
  }
  
  for (const [type, objOffset, gen] of xrefTableData) {
    offset = writeInt(type, sizes[0], offset, array);
    offset = writeInt(objOffset, sizes[1], offset, array);
    offset = writeInt(gen, sizes[2], offset, array);
  }
  
  writeString(footer, offset, array);
  return array;
}
export { incrementalUpdate, writeDict };