The nouns copy editor and copywriter are spelled this way. The verbs copy edit and copywrite are spelled as so. To avoid confusion—especially with compound words—I recommend using Merriam Webster's Dictionary, 11th Edition, the industry standard dictionary for spelling. If a word has multiple spellings, like “goodbye,” “good-bye,” and “goodby”, use the main entry. As part of each project, each author receives a customized Style Sheet that addresses spelling, among other things.