There are many different kinds of freelance editor jobs, and many different roles an editor can take, Following is a list of different kinds of editors/editing along with some hints for freelancers who are pursuing freelance editing jobs.
One caveat, many of these editorial roles interlap, or are simply in a state of flux. I've seen sources, publishers and authors call their project by one title, but the work described is a completely different thing. Since these kinds of edits are not completely cut and dry, freelance editors should always have specific duties fully described by their client, and then put into a freelance writing contract.
1. Acquistions Editor
An acquisitions editor is the person responsible for accepting, rejecting and finding manuscripts to publish within a specific publishing house. These are likely book-length manuscripts, fiction or nn-fiction. This editor must know their market and target audience, and make a call on what fits and what doesn't. In addition, this editor may be responsible for coordinating contracts and bringing authors on board. Sometimes this editor "follows" the manuscript through their publishing house, keeping track of its progress and remaining the first contact for the author. Freelance editors don't generally have opportunity to perform these types of duties, as they require a deep knowledge of the specific publishing house and are generally performed in house. However, I did find this blog entry about a freelance acquisitions editor from 2008, so you never know. I've also noted that many jobs are posted as freelance when in truth they are not. Be careful, do your homework, and check out the below types of editing.
2. Coordinating Editor
Also called a managing editor, the coordinating editor is like a traffic cop. Since a manuscript (whether book or magazine) is often touched by several people- writers, graphic designers, proofreaders, editors, photographers, translators, it is helpful to have one person “coordinate” by always knowing where the manuscript is and where it is going next. This can cut down on mistakes and wasted time. I know of several freelance editors who perform this job for magazines (although local publications seem to work best), getting manuscripts from writers to editors to graphics layouts as needed, and coordinating the entire collection of work for one issue on behalf of a publisher.
Copyediting is sometimes referred to as line editing, stylistic editing or mechanical editing. Copyediting focuses less on the content of a piece, and more on the mechanics, especially as they compare to the style guide in use. A copyedit checks things like spelling, grammar, sentence structure, and sometimes higher-level needs such as flow and consistency. Copyediting is one of the most common editing roles for freelancers, as it is needed for almost every manuscript, from web content to magazine articles to books, and is simple to perform remotely.
4. Comprehensive Editing
Also called developmental or substantive editing, and rarely also referred to as "macro editing," this type of editorial process deals with higher-level issues than copyediting. It specifically fixes the document at a content or structural level: paragraphs, pages, flow, organization, format, even as far as changing from first person to second person, improving characters (in books), fixing style issues and adding and deleting material. This can be performed by freelance editors, who often offer this service to authors and novelists, or self-published would-be authors, but it requires a good, proactive relationship with the author, as he/she is often heavily involved in this edit. If this can be established remotely, a freelance editor can perform well in this editorial role. Editors who are writers themselves, who are avid readers, or who have knowledge of the publishing industry would do well in this role.
5. Developmental Editing/Editor
This kind of editing has also been called comprehensive editing and substantive editing. See definition above for comprehensive editing, or below for substantive editing.In a nutshell, this editing involves further development of the work in high-level ways. This might mean working on plot, structure, or themes.
6. Fact Checking
Fact checking involves researching facts in a document, and verifying that they are true. This can be done via phone, internet or library. Freelancers can certainly excel in this role, with the right relationship to the publisher.
7. Format Edit
This type of edit focuses almost exclusively on the layout of a piece- graphics and font, etc. However, these same tasks are also dealt with by proofreaders. Freelancers can perform this edit.
8. Globalization/Translations Editing
This type of edit focuses on cultural/international issues that may be present in a document or manuscript. For example, at times translations are correct, but meanings are lost. This type of edit also looks at specific cultural items that vary by population such as how dates are written, how genders are presented, and how place names are given. Freelancers can perform this edit, and some specialize in certain languages or cultures.
9. Integrity Edit
An integrity edit focuses on the cross references that occur in large articles, such as journal pieces, and in non-fiction work. For example, if a manuscript notes "See table 3.1" the editor will verify that the table is present where it's supposed to be, and says what it's supposed to say. However, this edit is often performed by proofreaders, too. This edit is sometimes available to freelancers.
10. Line Edit
Line editing is undertaken to ensure that the document in its entirety has a true "flow." This means that we admit the author has likely written and rewritten (and/or already undergone a developmental edit). We also therefore acknowledge that these processes may cause flow issues, repetitions, or choppy language. Perhaps the cadence of paragraphs are at odds, because one was rewritten yesterday, when another was done a year ago. A line edit fixes these issues, which often come down to style issues. An interesting note, though is that the line edit has been compared to both a copyedit and a comprehensive or substantive edit. This plainly illustrates why it is so important to have good communication with your author.