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):

constructor(parameters) {
    super(parameters, { isRenderable: parameters.renderForms });
  }
  render() {
    this.container.classList.add("buttonWidgetAnnotation", "radioButton");
    const storage = this.annotationStorage;
    const data = this.data;
    const id = data.id;
    let value = storage.getValue(id, {
      value: data.fieldValue === data.buttonValue,
    }).value;
    if (typeof value === "string") {
      
      value = value !== data.buttonValue;
      storage.setValue(id, { value });
    }
    const element = document.createElement("input");
    GetElementsByNameSet.add(element);
    element.setAttribute("data-element-id", id);
    element.disabled = data.readOnly;
    this._setRequired(element, this.data.required);