Shredding newspaper has become my second hobby (next to vermicomposting). To provide bedding for my herd, I shred a lot of newspaper.
I like newspaper because it is free and plentiful. The papers come to my home and yesterday's paper is always available.
Office paper works equally well (for an office bin, your shredded office paper would work great). You want long strips, so a standard shredder works (but not a cross-cut shredder). Long, thin strips are better because cross-cut paper tends to mat when wet and you want your bedding to be airy.
Most non-glossy printed material can also be used since most high-quality laser toner and ink-jet inks are non-toxic. If you are going to use a lot of lot of a single source in your worm bin, check with the manufacturer to be certain. The Portland Press Herald uses non-toxic ink.
There is a technique to shred newsprint. I prefer to hold it by the folded edge (1-2 sections at a time) and shred into 1/8-1/4 inch strips. It shreds really easily and it makes a nice swooshing sound. For a long time Bert thought I was sweeping every morning!
Another advantage of newspaper is that shredding it is relaxing. It sounds strange, but I shred A LOT of newspaper, and I have come to enjoy this quotidian task. It is a morning activity I appreciate after I feed my herd. I shred yesterday's paper in the cellar and listen to NPR while I sip my coffee. It is a few minutes of meditation before I start my day.