property PageShadowColor: TColor; // default clGray
Each page in the viewer is drawn as a rectangle floating over the control's Color background. Below the right and bottom edges of that rectangle the viewer paints a drop shadow strip that visually lifts the page off the scroll area, mimicking the look of Adobe Reader and other modern PDF viewers. PageShadowColor is the solid fill of that strip.
The shadow is only rendered when PageShadowSize is greater than zero. With PageShadowSize set to 0 the colour is ignored and no extra pixels are drawn, which is the default appearance (flat, no shadow).
Pick a colour darker than Color to get a believable shadow. clGray, $00606060 (charcoal), or a custom 30%-luminance grey all read convincingly. Lighter colours on a light background reduce the effect to a subtle border accent.
PageColor = clWhite with PageShadowColor = clGray and PageShadowSize = 6.Color = $00202020, PageColor = clWhite, and PageShadowColor = $00000000 to keep contrast high.// Classic Adobe-style page presentation.
PdfView1.Color := $00CCCCCC; // light grey scroll area
PdfView1.PageColor := clWhite;
PdfView1.PageShadowSize := 6;
PdfView1.PageShadowColor := clGray;
PdfView1.PageBorderColor := $00808080;
// Crisp, high-contrast page edge for dark mode.
PdfView1.Color := $00202020;
PdfView1.PageShadowColor := clBlack;
PdfView1.PageShadowSize := 8;