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("hasFillAlpha");
        }
      }
    }
    trigger.addEventListener("dblclick", this.#download.bind(this));
    this.#trigger = trigger;
    const { isMac } = FeatureTest.platform;
    container.addEventListener("keydown", evt => {
      if (evt.key === "Enter" && (isMac ? evt.metaKey : evt.ctrlKey)) {
        this.#download();
      }
    });
    if (!data.popupRef && this.hasPopupData) {
      this._createPopup();
    } else {
      trigger.classList.add("popupTriggerArea");
    }
    container.append(trigger);
    return container;
  }
  getElementsToTriggerPopup() {
    return this.#trigger;
  }
  addHighlightArea() {
    this.container.classList.add("highlightArea");
  }
  /**
   * Download the file attachment associated with this annotation.
   */
  #download() {