A master document lets you manage large documents, such as a book with many chapters. The master document can be seen as a container for individual LibreOffice Writer files. The individual files are called sub-documents.
When you print a master document, the contents of all sub-documents, indexes, and any text that you entered are printed.
You can create a table of contents and index in the master document for all of the sub-documents.
Styles that are used in sub-documents, such as new paragraph styles, are automatically imported into the master document.
When viewing the master document, styles that are already present in the master document take precedence over styles with the same name that are imported from sub-documents.
Sub-documents never get changed by changes made to the master document.
When you add a document to a master document or create a new sub-document, a link is created in the master document. You cannot edit the content of a sub-document directly in the master document, but you can use the Navigator to open any sub-document for edit.
A master document master.odm consists of some text and links to the sub-documents sub1.odt and sub2.odt. In each sub-document a new paragraph style with the same name Style1 is defined and used, and the sub-documents are saved.
When you save the master document, the styles from the sub-documents are imported into the master document. First, the new style Style1 from the sub1.odt is imported. Next, the new styles from sub2.odt will be imported, but as Style1 now already is present in the master document, this style from sub2.odt will not be imported.
In the master document you now see the new style Style1 from the first sub-document. All Style1 paragraphs in the master document will be shown using the Style1 attributes from the first sub-document. However, the second sub-document by itself will not be changed. You will see the Style1 paragraphs from the second sub-document with different attributes, depending whether you open the sub2.odt document by itself or as part of the master document.
To avoid confusion, use the same document template for the master document and its sub-documents. This happens automatically when you create the master document and its sub-documents from an existing document with headings, using the command File - Send - Create Master Document.