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specified in the [commit comment](https://github.com/mozilla/pdf.js/commit/8de98079ca05f8f7001ee077771055a57dc0e948) is outdated.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There are probably other problems with that code due to the outdated spec @calixteman was apparently working on.
fileInput.setAttribute("type", "file");
    fileInput.oncontextmenu = noContextMenuHandler;
    document.body.appendChild(fileInput);
    if (
      !window.File ||
      !window.FileReader ||
      !window.FileList ||
      !window.Blob
    ) {
      appConfig.toolbar.openFile.setAttribute("hidden", "true");
      appConfig.secondaryToolbar.openFileButton.setAttribute("hidden", "true");
    } else {
      fileInput.value = null;
    }
    fileInput.addEventListener("change", function (evt) {
      const files = evt.target.files;
      if (!files || files.length === 0) {
        return;
      }
      PDFViewerApplication.eventBus.dispatch("fileinputchange", {
        source: this,
        fileInput: evt.target,
      });
    });
    
    appConfig.mainContainer.addEventListener("dragover", function (evt) {
      evt.preventDefault();
      evt.dataTransfer.dropEffect = "move";
    });
    appConfig.mainContainer.addEventListener("drop", function (evt) {