Some of the PDF.js code mentions an "annotation layer", for example AnnotationLayerBuilder here:

https://github.com/mozilla/pdf.js/blob/95e102c07bc257c2120fd7fd9141762b2c813a1c/web/annotation_layer_builder.js#L118

There is also pdfDocument.annotationStorage and pdfjsLib.AnnotationLayer, which - on all the documents I've tried - are empty, even in documents which do have text annotations.

I couldn't find any examples or documentation on the annotation layer and how it is supposed to be used, but it sure sounds interesting :)

1. What is the annotation layer? Is this talking about standard PDF annotations, as described in https://pspdfkit.com/blog/2018/what-are-annotations/ or https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/pdf_reference_1-7.pdf section 8.4 Annotations? Or, is it something internal to PDF.js?

   
   



2. How do I list the existing annotations from javascript code in PDF.js, and how do I add one? (just for display; not expecting to be able to save it in the pdf, of course) Can anyone provide a working code example?

   
   

Thanks!