This is the 13063rd most frequent Russian word.
марать
To soil, dirty, or stain.
Here, 'марать' is used to mean 'soil' or 'stain' in a figurative way, referring to adding unnecessary notes to paper.
Не стоит марать бумагу лишними записями.
It is not worth smudging the paper with extra notes.
In this context, 'марать' refers literally to the act of soiling or staining clothes with dirt or mud.
Дети любят марать одежду на прогулке.
Children love to dirty their clothes during a walk.
Here, 'марать' is metaphorically used to mean 'tarnish' or 'damaging' one's reputation.