Because the length of a form that has a flexible layout varies depending on the amount of data merged with the form, forms that have a flexible layout are often longer than one page. Using overflow leader and overflow trailer subforms is an effective way to start and finish subforms that repeat over multiple pages. You can use any subform that is configured to position content as an overflow leader or trailer. For example, in the Purchase Order sample form, the detail subform is configured to position content and repeat for every data item. When the form is merged with data, if the first page has sufficient space to display all occurrences of the detail subform, a new page is added and the data continues to flow into the next content area.
When data flows this way across multiple pages, you may want to carry forward onto each new page certain text such as “Continued from previous page” or specific formatting elements such as a column header row that includes the descriptive labels for each column of data. Using column header rows on each subsequent page makes the resulting form much easier for users to follow. To do this, you can create an overflow leader subform that will act as the column header row for each additional page. In the Purchase Order sample form, for example, the detailHeader subform is selected as the overflow leader. As a result, a copy of the detailHeader subform is rendered at the top of every new page before the first occurrence of the detail subform.