property Zoom: Double;
Zoom factor where 1.0 = 100% (one PDF point equals 1 screen pixel at 72 DPI)
Assigning a value automatically switches FitMode to pfmNone
All TPdfView display properties schedule a repaint when assigned; several changes in sequence are folded into a single invalidation, so the control redraws once rather than flickering
Active := TruePdfView1.Pdf at runtime, reapply any view-only settings — the new TPdf has its own state
begin
PdfView1.Zoom := {value};
PdfView1.Active := True;
end;