Pages won't open after unexpected shut down

I'd try clearing the saved state files.

From Finder:

  • Cmd ⌘ N
  • Cmd ⌘ Shift ⇧ G
  • Copy/paste ~/Library/Saved Application State

Find the folder com.apple.iWork.Pages.savedState and delete the contents not the folder itself, as it's an alias.
That should give Pages a fresh start.