property Zoom: Double;
Zoom factor where 1.0 = 100% (one PDF point = 1 screen pixel at 72 DPI).
Assigning a value implicitly switches FitMode to pfmNone.
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.Zoom := {value};
PdfView1.Active := True;
end;