You may want to start working on a workflow in a space which already contains several pages. If the workflow you want to enable as a space workflow restricts the view of unapproved pages, you would have to approve each page so they can be viewed by read-only users.
That's why you have the option to initialize the states of existing pages when working with space workflows.
Only Space and Confluence administrators can initialize spaces.
Go to Space Administration > Workflows and in the Space workflows section. Click Initialize states from the action menu.
Select the initial state for each page in the space. By default, only pages that have not gone through the workflow are initialized. You can override existing states for all the pages.
Depending how many pages you have in the space, it may take a while. The progress will be displayed on the following screen.