property ActualSizeZoom: Double;
Read-only zoom factor that displays the page at its true physical size on the host screen.
Computed using the OS-reported screen DPI and the page's width/height in points.
All TPdfView display properties trigger a repaint when assigned; you can change several in sequence without flicker because the redraw is coalesced into a single invalidation.
Active := True.PdfView1.Pdf at runtime, re-apply any view-only settings — the new TPdf has its own state.
begin
PdfView1.ActualSizeZoom := {value};
PdfView1.Active := True;
end;