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 TEXT_ALIGNMENT = ["left", "center", "right"];
    const { fontColor } = this.data.defaultAppearanceData;
    const fontSize =
      this.data.defaultAppearanceData.fontSize || DEFAULT_FONT_SIZE;
    const style = element.style;
    
    
    
    
    
    
    
    
    let computedFontSize;
    const BORDER_SIZE = 2;
    const roundToOneDecimal = x => Math.round(10 * x) / 10;
    if (this.data.multiLine) {
      const height = Math.abs(
        this.data.rect[3] - this.data.rect[1] - BORDER_SIZE
      );
      const numberOfLines = Math.round(height / (LINE_FACTOR * fontSize)) || 1;