Files (.pages / .numbers / .key) created by iWork cannot be directly uploaded via browsers. You will need to export the file in a ZIP archive before uploading:
- From the “File” menu, choose “Export To” > “ZIP Archive”.
- Select a location to save the file.
For more information, please check the Apple website iWork for Mac: Exporting files into a ZIP archive (http://support.apple.com/kb/HT6073?viewlocale=en_US)