Use Word's Accessibility Checker as you create or edit a document. The Accessibility Checker should automatically run in the background and give alerts in the status bar as it finds issues. If it isn't, manually launch the Accessibility Checker by clicking Review - Check Accessibility.
Headings are crucial for screen-readers to be able to read the text on the screen efficiently no matter what format the text is in (Word, PDF, web pages). When you click a heading style, Word applies a font and color change to help make it clear that the affected text is actually a title of a document or subsection but, behind the scenes, it's also adding tags that screen readers will recognize. To add a heading style:
Watch the video, Improve accessibility with heading styles, to see why it's important to use headings and how to do so.
Formatting in APA style? Please refer to the official Accessibility of APA Style guide.
Do this instead of Print - Save as PDF .