"Double space between all text lines of the document," says APA Manual, 6th edition, p. 229. Each line of a printed page should have enough room to contain not only punctuation marks and words but also spaces for inserting sheets if the page is not single-sided.
The answer depends on what kind of paper you use. If you print on 8.5 x 11 inch sheet, then yes, it is double-spaced. But if you use A4 paper, then it is single-spaced - like most books. There is no standard size for pages in an academic journal, so each one is double-spaced.
When writing articles for publication, it is customary to provide more than one copy - called an "edition" - for review and comment. The final version of the article should be published with the same number of copies as there were editions created for review. So for example, if you publish an article in a book with five other authors, then it is usual to produce six copies of the article: three for review by journals and universities and three more for distribution to readers.
In general, double-spacethe abstract, text, block quotes, table and figure numbers, titles, and notes, and reference list in an APA Style document (including between and within entries). There should be no excess space before or after paragraphs. Single spacing is used for the rest of the body of the paper.
The answer to this question depends on your audience and the type of paper you are writing. If you are writing for a scientific journal that requires two pages for references, then you should include references in a separate section at the end of your paper rather than including them within the text. Also, remember that an abstract is usually only one page long so it too should be written with no margin space around it.
Overall, APA recommends that you write with two spaces after each period, sentence punctuation, and paragraph break. This will make your paper look more professional and give it a less typewriter-like feel.
APA Style recommends double-spacing throughout a manuscript as the usual line spacing. If your work requires a section that is not covered in this post or in the publishing manual, we recommend that you use double spacing unless otherwise advised.
Single spacing should be used when writing a novel or short story. It makes for a more compact document and can help to increase the impression of speed and urgency when writing a crime scene report or medical diagnosis. When writing a paper for class or employment, single spacing is recommended.
When writing a book, reporters often refer to the amount of space between lines of type as "line height." Line height is the term used to describe the point at which lines of type begin to converge. For example, if you double space a document, the line height will be half of the font size. If you use 10-point type, then the line height will be 5 points.
Generally speaking, the closer the line height is to the point size, the better. This allows for more words on a page, which can lead to a longer read but also a more impressive-looking one. At times, however, such as when using small print or when placing text inside other elements such as illustrations or tables, it may be necessary to reduce the line height or even set it to a smaller value than default.