property PageBorderColor: TColor;
Colour of the 1-pixel border drawn around each page rectangle.
Use clNone to disable the border (visual control only — PDF content is unaffected).
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.PageBorderColor := {value};
PdfView1.Active := True;
end;