property Canvas: TCanvas;
Drawing canvas exposed by the control after a page is rendered
Use in OnPaint to overlay custom graphics on the rendered page
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.Canvas := {value};
PdfView1.Active := True;
end;