@Ana1234 - I imagine they have to bleach it and process it a little bit more in order to make it at the quality that people expect. The problem with recycling paper is that it can't really be done indefinitely. The fibers become shorter every time and so the paper needs to be thicker and rougher to hold its shape.
They usually either mix in raw materials or they jump through hoops to make the paper work.
With that said, there is actually no need to chew up trees in order to make paper. It can be made from all kinds of byproducts, like those from bamboo and sugar cane, as well as from other plants like hemp. Considering how much faster those kinds of plants grow, it actually seems like a waste of time to use trees, even from a financial point of view. But, unfortunately, even non-THC containing hemp is usually illegal.