"All errors will be faithfully reproduced," appears over my desk.
You are not a copy writer, unless you are. There are different kinds of "editing," to confuse the issue.
As the graphic designer in a specialized field, you may be, or soon to be, familiar with the terminology enough to do what your client expects of you. That may not be the case for any one of a number of reasons now. That expected increased level of expertise usually comes at a premium.
Let's step back a bit and look for a more appropriate way to describe what is wanted/needed/required. I think the issue is fuzzy. Normally, I would suggest using place-holder text (greeking) for the look-and-feel of a layout pending approval of final copy writing. If the layout and copy don't match, I'm obliged to submit a new/updated layout to accommodate the provided copy. Sometimes, the copy is edited to fit the layout. This time-saver usually costs more time and causes more trouble than any saving.
As the graphic designer — I take responsibility for the original design or concept development for the layout.
Publishing — I take responsibility for incorporating correct, approved, formatted text and graphics into polished, effective layouts using publication software.
Straight Proofreading — I will compare two versions of a document to catch typographical errors and deviations from format instructions, questioning blatant errors and inconsistencies.
Editorial Proofreading — Proofreading by looking at only one version of a document; a step between proofreading and copyediting. Checking for typos, consistency of style and format, basic grammar, internal agreement, and overall sense — not including rewriting.
Copyediting — Reviewing a manuscript for spelling, grammar, consistency of style and format. May include. checking completeness, accuracy, and format of tables, bibliographies, and footnotes — not including rewriting.
Substantive Editing — Rewriting, reorganizing, and reviewing content for accuracy and logic; ensuring proper tone and approach for intended audience.
Writing — Producing a manuscript by working from supplied materials, conducting research or interviews; planing; preparing outlines, drafts, and summaries; attending meetings; consulting; and making revisions.