Document Outline (a.k.a Bookmarks)

PDF defines document outline (PdfOutlineNode), which is sometimes called as bookmarks or index. And you can access it by PdfDocument.loadOutline.

The following fragment obtains it on PdfViewerParams.onViewerReady:

onViewerReady: (document, controller) async {
  outline.value = await document.loadOutline();
},

PdfOutlineNode is tree structured data and for more information, see the usage on the example code.