The felt side is a normal byproduct of the papermaking process, but paper to be printed on both sides can be given a felt finish on the wire side as well by pressing a felt blanket against the wire side before the water content is removed or by embossing dry paper. (AllBusiness.com, Inc. )

There are several known causes of inherent curl in paper. For example, the wire side and felt side of a sheet exhibit different degrees of fibre orientation, with wire side fibres tending to be more aligned in the machine direction than felt side fibres. (PaperlinX )

Mohawk papers are packed Felt side up in cartons and reams. (The paper mill store.com)