The Reorder/Add Pages function - available only for Presentations - allows you to delete or rearrange the pages of a presentation or personal presentation template in addition to adding pages from any other presentation template in your library.
There are several rules governing adding pages to a presentation. More Info:
Add and/or reorder pages:
Open the View Presentation (for existing presentations) or the Edit Personal Copy (for presentation templates) screen. How?
Click the Reorder/Add Pages link at the top of the page.
From the Reorder/Add Pages screen you can:
Find a page from another template by selecting the presentation's Category, Template and the page from the Add Page portlet. Then drag and drop the page you want into the spot within your current presentation/template.
Remove a page by clicking its Delete icon.
To reorder pages, drag and drop the pages to their desired locations.
Click the Done button to save your changes and return to the Edit Personal Copy or View Presentation screen.