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):

parentRect,
    open,
  }) {
    this.#container = container;
    this.#titleObj = titleObj;
    this.#contentsObj = contentsObj;
    this.#richText = richText;
    this.#parent = parent;
    this.#color = color;
    this.#rect = rect;
    this.#parentRect = parentRect;
    this.#elements = elements;
    const dateObject = PDFDateString.toDateObject(modificationDate);
    if (dateObject) {
      
      
      
      this.#dateTimePromise = parent.l10n.get("annotation_date_string", {
        date: dateObject.toLocaleDateString(),
        time: dateObject.toLocaleTimeString(),
      });
    }
    this.trigger = elements.flatMap(e => e.getElementsToTriggerPopup());
    
    for (const element of this.trigger) {
      element.addEventListener("click", this.#boundToggle);
      element.addEventListener("mouseenter", this.#boundShow);
      element.addEventListener("mouseleave", this.#boundHide);
      element.classList.add("popupTriggerArea");
    }