Header and other parts used many times in a project are turned into common parts as "Symbol". When you symbolize a box, you can also apply the edits to the other symbolized box at once.
To symbolize a box you have created, select it, right-click on it and select Symbolize or select it and press ⌘+J.
Placing the Symbols
In the Symbols tab of the Add Panel, you can find a list of symbols you've created and you can drag and drop them onto the canvas.
You can edit placed symbols by double-clicking on them when they are selected. If you edit a symbol anywhere, all changes, including text and images, will be applied to all placed symbol boxes and the original on the symbol panel.
Detach the symbol
If you want to detach a placed symbol box and use as a normal box, press ⌘+Shift ＋J.
When you detach, the original symbol and other placed symbol boxes remain intact.