If you want to edit an existing brochure, select the desired brochure in the PDFdesigner.
With older PDF brochures, not all functions are available in some cases. These are limited to the displayed functions. If you are missing features, you will need to recreate these brochures.
Make your changes by clicking on each page and changing the settings. Click on Basic settings of this brochure to get to the basic settings if you want to make changes there.