How can I read and edit files from Apple iWork (Keynote, Pages)?
There is no universal "Mac format". Applications have their own file formats for storing data.
An office suite for Ubuntu is LibreOffice. To allow for document exchange, save the file in a format understood by both programs:
- Keynote / LibreOffice Impress:
.ppt - Pages / LibreOffice Writer:
.doc - Numbers / LibreOffice Calc:
.xls
Pages file is actually a .zip archive, there's a handy blogpost here http://blog.cleverly.com/permalinks/346.html