If you want a hole in the bookmark, add a negative part (cylinder) and adjust his size and position in the model. In the print project, the negative part is inserted.

Model size is 50x150mm. When changing dimensions, you must not change the height (Z).

Print at 100% infill with a layer height of 0.08mm with a base layer of 0.16mm.

Filaments Used:
PLA Elegoo + Black Transmission Distance: 0.3
PLA Elegoo + Space Gray Transmission Distance: 2.4
PLA Devil Design Light Brown Transmission Distance: 1.6
PLA Elegoo + White Transmission Distance: 7
 

Swap Instructions:
Start with Black
At layer #8 (0.72mm) swap to Space Gray
At layer #14 (1.2mm) swap to Light Brown
At layer #17 (1.44mm) swap to White for the rest.