Can Pages 5 (a.k.a. Pages '13) import Pages '08 documents?
According to Ars Technica's iWork '13 review, Pages '13 can't open '08 documents.


  The iWork '13 apps on the Mac can open iWork '09 files but not iWork '08 files.


If you still have a copy of Pages '09 you could save the documents in '09 format and then use '13 to save them in '13 format.