pageNumber: the physical page index (1-based) within the PDF document.
pageLabel: optional printed page label shown by PDF viewers (e.g. "iii", "1", "A-1");
this can differ from the physical page number and may be undefined
when the document does not provide labels.
links: array of text->URL mappings that were found/overlaid on the page.
width/height: page dimensions in PDF units for the viewport used.
Per-page link extraction result.