When you synchronize documents in a book, the items you specify—styles, variables, master pages, trap presets, numbering lists, and swatches—are copied from the style source to the specified documents in the book, replacing any items that have identical names.
If items in the style source are not found in the documents being synchronized, they are added. Items that are not included in the style source are left as is in the documents being synchronized.
For a video on synchronizing book documents, see www.adobe.com/go/vid0216.
You can synchronize the book while documents in the book are closed. InDesign opens the closed documents, makes any changes, and then saves and closes the documents. Documents that are open when you synchronize are changed but not saved.
Master pages are synchronized in the same way as other items—master pages with the same name (such as A-Master) as those in the style source are replaced. Synchronizing masters is useful for documents that use the same design elements, such as running headers and footers. However, if you want to preserve page items on a master page in documents other than the style source, either don’t synchronize master pages, or create master pages with different names.
Any master page items that are overridden on document pages before you synchronize masters for the first time are detached from the master. Therefore, if you plan on synchronizing master pages in your book, it’s a good idea to synchronize all the documents in your book at the start of the design process. That way, overridden master page items will maintain their connection to the master page and will continue to be updated from modified master page items in the style source.
It’s also a good idea to synchronize master pages using only one style source. If you synchronize from a different style source, overridden master page items may become detached from the master page. If you need to synchronize using a different style source, deselect the Master Pages option in the Synchronize Options dialog box before doing so.