Self-editing is the task of editing your own document after you have written it. After self-editing, some types of documents also need to be edited and/or proofread by another person.
If your document isn't important or formal and doesn't need to be professionally presented, you probably don't need another person to edit your document. You simply need to write it, self-edit it, then either proofread it yourself or ask someone to proofread it for you. This is self-editing. The final product may not be entirely clear and may contain spelling or punctuation errors but if this doesn't matter to you or, importantly, to the person to whom you are submitting the document, then there is no need to have it edited properly.
The types of documents that you would usually edit yourself (rather than asking someone else to edit it for you) are minutes of informal meetings, essays for school or tertiary assessment, and informal articles and posts on social media. You should also be aware that if your document is an essay or article intended for assessment by an academic institution, or a piece of writing you are submitting to a competition, you may be required to edit the document yourself (although it is usually permissable to have someone else proofread your work).
Note: self-editing alone is not going to produce a piece of writing to the standard required for publication. You will need a professional editor to do this.
If you have written a job application, resume, newsletter, article, policy document or a report that is going to be read by an interview panel, or the manager or staff of your organisation, I suggest that you ask someone else to edit your document. This person does not need to be a professional editor; if you have a friend or colleague that you know is particularly good at writing or editing and experienced in editing others' work, you could ask him/her to edit the document for you. The document will then need to be proofread by someone other than yourself or the person who has edited the document; if you have a friend or colleague with really good knowledge of grammar, spelling and punctuation and some experience in proofreading, you could ask him/her to proofread your document. Finally, after all the corrections have been made, I suggest you carefully proofread document yourself one last time before submitting it. Even though the document has not been corrected by professional editors or proofreaders and is not likely to be perfect, it will be of a far higher standard than if you had merely edited and proofread the document yourself.
Note: getting a non-editor colleague to edit your document is not going to produce a piece of writing to the standard required for publication. You will need a professional editor to do this.
If your piece of writing is intended for publication or needs to be presented professionally - e.g. a report, submission to an inquiry, article, policy, or fiction or non-fiction manuscript - after you have self-edited it to the stage where you can improve it no more, it should be edited by a professional editor to make sure it is well-designed and error-free.
For more information about this topic go to: Why writers need editors
For information about how to self-edit your manuscript before handing it to an editor, go to: Self-editing your manuscriptThis article is based on my own experience over the last 20-something years, editing and proofreading reports, policy documents, and my own and others' publications; self-publishing hardcopy publications; and publishing my website and articles online. Keep posted for future articles about editors and editing, proofreaders and proofreading.