In LibreOffice Draw we can import a PDF with PDFium, where each PDF page is imported as an image and added into each Draw page. The PDF annotations are then added separately as comments, so they can be added and modified separately to the PDF. The issue is that the PDF annotation support is much more extensive than what is supported by LibreOffice Draw.

There are many types of annotations in PDF: line, rectangle, polygon, stamp(image), highlight, in-line text,... In LibreOffice Draw we only support one type of annotations - pop-up text (comment). To support PDF annotations in LibreOffice Draw, it is necessary to change how the annotations are stored in the document model, which is now very similar to the objects in the document (with the exception that the annotations aren't normally visible when printing). The user should be able to move, resize the annotations, change properties (line, background text color,...), edit text...