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):

this.container.classList.add("popupAnnotation");
    const popup = new PopupElement({
      container: this.container,
      color: this.data.color,
      titleObj: this.data.titleObj,
      modificationDate: this.data.modificationDate,
      contentsObj: this.data.contentsObj,
      richText: this.data.richText,
      rect: this.data.rect,
      parentRect: this.data.parentRect || null,
      parent: this.parent,
      elements: this.elements,
      open: this.data.open,
    });
    const elementIds = [];
    for (const element of this.elements) {
      element.popup = popup;
      elementIds.push(element.data.id);
      element.addHighlightArea();
    }
    this.container.setAttribute(
      "aria-controls",
      elementIds.map(id => `${AnnotationPrefix}${id}`).join(",")
    );
    return this.container;
  }
}
class PopupElement {