Question:
It is Shabbos. Somebody is reading a page that was written (or printed) in ink. He finds an error and crosses it out with a pen.
Does this fall under a specific issur? He hasn't written anything (כותב), and he has not cleared any space in order to write anything (מוחק).
Answer:
He is transgressing the rabbinic issur of "mekalkel".
Sources:
Shabbos 106a
