For detailed instructions on this issue in Word 2013 or 2016, click here.
The following instructions apply to only Word 2013:
When you apply heading styles to your document and hover your mouse over that heading, a gray arrow will appear to the left of the heading. This will allow you to expand or collapse all of the text under that heading.
When you reopen a document it will default to expanded. To change this, click on and open the paragraph settings and check the box for collapsed by default
There is a quick way to expand or collapse all headings in your document; right click on a heading > Expand/Collapse, and select Expand all Headings or Collapse all Headings.
For a Quick 1 minute YouTube tutorial and additional information use the links below.