What a PdfView shows: the current page, the page count, the zoom and whether it is still working.
public PdfViewState(int PageIndex, int PageCount, double Zoom, bool IsLoading, bool IsRendering)
The page at the viewport's centre (zero-based).
The document's page count (0 while nothing is open).
The zoom relative to the page's actual size (1 = 100 %).
Whether a document is being opened.
Whether tiles the viewport wants are still being drawn.
ISO 32000-2 §14.11.2 (page boundaries: the zoom's actual size is one point per 1/72 inch).