- Open the master document (master document: A "container" for a set of separate files (or subdocuments). You can use a master document to set up and manage a multipart document, such as a book with several chapters.) and click Outline on the View menu.
- If the subdocuments are collapsed, click Expand Subdocuments on the Outlining toolbar (toolbar: A bar with buttons and options that you use to carry out commands. To display a toolbar, press ALT and then SHIFT+F10.).
- Click where you want to add the existing document.
Make sure to click a blank line between existing subdocuments.
- On the Outlining toolbar, click Insert Subdocument .
- In the File name box, enter the name of the document you want to add, and then click Open.
Microsoft Word inserts a next page section break (section break: A mark you insert to show the end of a section. A section break stores the section formatting elements, such as the margins, page orientation, headers and footers, and sequence of page numbers.) before the subdocument and a continuous section break after it.