Pages 5 has an orange document icon.
Pages '09 has a blue ink bottle icon.
This is the full story:
You have 2 versions of Pages on your Mac and are alternately opening the wrong one.
Pages 5 is in your Applications folder.
Pages '09 is in your Applications/iWork folder.
Pages '09 can not open Pages 5, iOS 7 Pages, Pages for iCloud beta or iCloud files.
Pages 5 only runs on Mavericks and can not open Pages '08 or earlier files at all and alters/damages Pages '09 files, which once saved can not be opened by anything other than Pages 5.
Pages 5 files are in an odd compressed bundle, impossible to parse, which won't transfer via non-Apple servers. DropBox may have patched theirs, I haven't checked lately.
All Pages files, no matter what version or compatibility, have the same file extension: .pages.
Apple has removed over 110 features from Pages and many of the rest are buggy. They have confused their users and apparently themselves with the installations, upgrades and cross-transfers of files. Effectively Pages 5 files are only compatible with themselves in a very narrow range of hardware and software.
http://www.freeforum101.com/iworktipsntrick/viewforum.php?f=22&mforum=iworktipsn trick
You can trash Pages 5 after Menu > File > Export > Pages '09 any files you converted to Pages 5.
Just drag Pages 5 to the Trash.
Peter