watermark (alias mark).

Bottom-right mark — ?watermark={fileId}&markW=160&markOpacity=0.72.

Top-left anchor — ?markPosition=top-left&markW=140.

Subtle bottom-center — ?markScale=22&markOpacity=0.4.

Rotated center mark — ?markRot=45&markW=180.

Tiled grid — ?markScale=18&markRot=30&markTile=grid&markGap=64.

Multiply blend — ?markBlend=multiply&markScale=28.