This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
The Centronics interface is the standard parallel interface for many printers. To connect such a printer to an Apple II, you need a printer interface card and cable. Since the cards were a popular item in the early 80's and were produced by several different companies you should be able to get a good one without too much trouble. The cards turn up fairly often at swap meets, should be easy to find on comp.sys.apple2.marketplace, and are still sold by regular A2 vendors. MC Price Breakers (360-837-3042 Mon-Fri 9:30am-5:30pm Pacific Time) offers a "Full Text & Graphic Interface" w/cable for Centronics type parallel printers for $29.95.