Edited academic writing can be found in various places, depending on the type of writing you are looking for.
If you are looking for edited articles and essays, typically these can be found in peer-reviewed journals and research databases, such as JSTOR, EBSCOhost, or Academic Search Premier. Many universities and other research institutions have subscriptions to these databases, which allow students and faculty to access their resources for free. You can also search for and purchase edited academic articles from individual websites.
If you are looking for edited course materials, such as lecture notes, quizzes, and examinations, these may be available from a variety of websites. Usually, educational websites, such as Coursera, Khan Academy, and Udemy, will have edited course materials. You can also search for course materials on sites like Teachers Pay Teachers or Your Step by Step.
Finally, if you are looking for edited textbooks and study guides, you can find these in any online bookseller. Amazon, Barnes & Noble, and other online booksellers often have various editions of textbooks and study guides.
Overall, there are many places to find edited academic writing, depending on what type of writing you are looking for.