Let $F$ be a coherent sheaf on $\mathbb{P}^n$. Why do there exist integers $N$ and $p$ such that there is a surjection $\mathcal{O}_{\mathbb{P}^n}(p)^{\oplus N}\rightarrow F\rightarrow 0\;?$
I might be misinterpreting a book, so if the above is false, then what would a similar true statement be?