While working with your report you can see the new item in the left menu, called Report Tabs, and Add Tab button underneath. Each tab is a separate dashboard where you can place any widgets you want, choose different filters, etc. but still keep using the same data set. When you create a PDF-file to print or send your report somewhere, you can create separate files for different tabs.
A good example of using Report tabs is creating an annual report where every tab is dedicated to one month and use own date range. You can add a new clear dashboard to your report by pressing Add Tab button. It will allow you to structurize your report better. Also, export to PDF allows you to print only the current tab.
You can rename your tabs and also you can clone any tab you want (ie.g. if you want a report having one tab for each month you can create one tab, set up all necessary widgets and then just clone this tab 11 times and edit date intervals in the filter). To see editing and cloning functions you need to point your mouse cursor over the tab.
Two icons will appear.
Left one allows you to reorder your tabs in the list. When you click left mouse button on it, you can drag your tab up and down until you release the button. When you click the right one (a gear icon) it allows you to rename, clone or delete the tab (you cannot delete the last existing tab in the report).