While Web Builder 2.x only supported one page per file, in version 5.x you can have multiple pages in a single file. Instead of putting all your pages into different files you now must manage the pages from the Site Manager, where you can add, edit, remove, clone and rename them.
See also: http://www.wysiwygwebbuilder.com/introduction.html
To open existing Web Builder 2.x files in Web Builder 5 follow these instructions:
First you'll need to open a new web site to be able to import existing pages. To import pages created with a previous version of Web Builder:
1. File->New Web Site
2. A new project (Web Site) will open.
3. Note that there's already one empty page called 'index', you can remove that later (a web site always has a minimum of 1 page)
4. Now you can import all your exisiting pages by selecting Page->Import->Import Web Builder 2.x page from the menu.
You can import all your existing files in a single project.
To rename the imported pages select the page name in the Site Manager en press F2 or right click to display context menu.