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 setColor = (jsName, styleName, event) => {
      const color = event.detail[jsName];
      const colorType = color[0];
      const colorArray = color.slice(1);
      event.target.style[styleName] =
        ColorConverters[`${colorType}_HTML`](colorArray);
      this.annotationStorage.setValue(this.data.id, {
        [styleName]: ColorConverters[`${colorType}_rgb`](colorArray),
      });
    };
    return shadow(this, "_commonActions", {
      display: event => {
        const { display } = event.detail;
        
        
        const hidden = display % 2 === 1;