Reading from the source code:

https://github.com/mozilla/pdf.js/blob/57d196e3497e77c81c19f852715ce79d9fb91492/src/display/annotation_layer.js#L2846

it appears to me it was not an intention to mark downloadManager as a required parameter in AnnotationLayerParameters:

https://github.com/mozilla/pdf.js/blob/57d196e3497e77c81c19f852715ce79d9fb91492/src/display/annotation_layer.js#L63

and AnnotationLayerBuilderOptions:

https://github.com/mozilla/pdf.js/blob/57d196e3497e77c81c19f852715ce79d9fb91492/web/annotation_layer_builder.js#L40

and it should be optional, similarly to accessibilityManager for example:

https://github.com/mozilla/pdf.js/blob/57d196e3497e77c81c19f852715ce79d9fb91492/web/text_layer_builder.js#L30

**Configuration:**
- PDF.js version: 2.11.174
- Is a browser extension: no

**What is the expected behavior? (add screenshot)**

`downloadManager` to be optional

**What went wrong? (add screenshot)**

`downloadManager` marked as required

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

const { container, data } = this;
    container.setAttribute("aria-haspopup", "dialog");
    const popup = new PopupAnnotationElement({
      data: {
        color: data.color,
        titleObj: data.titleObj,
        modificationDate: data.modificationDate,
        contentsObj: data.contentsObj,
        richText: data.richText,
        parentRect: data.rect,
        borderStyle: 0,
        id: `popup_${data.id}`,
        rotation: data.rotation,
      },
      parent: this.parent,
      elements: [this],
    });
    this.parent.div.append(popup.render());
  }
  /**
   * Render the annotation's HTML element(s).
   *
   * @public
   * @memberof AnnotationElement
   */
  render() {