property PageShadowSize: Integer;
Width (in pixels) of the soft shadow drawn around each page in continuous modes.
Set to 0 for a flat look or 6+ for a deep Acrobat-style drop shadow.
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.PageShadowSize := {value};
PdfView1.Active := True;
end;