Final answer:
The space between the main title and secondary title should follow the specified format in the style guide being used; MLA does not require extra space, while APA standards for titles on a title page indicate bold and centered formatting for the main title, with subsequent titles following as outlined.
Step-by-step explanation:
When formatting a paper, the space between the main title and the secondary title is generally determined by the style guide you are following. In MLA format, you should not add extra space below the main title before the secondary title, which means they should be double-spaced, just like the rest of the paper. In APA format, titles and subtitles are often part of a title page or at the beginning of a paper, where the main title is bold and centered, and the secondary title (which may serve as a section heading) is also bold but aligned to the left, following any applicable spacing guidelines.