Email pages documents from Mail app

Under ios9, is it possible to include Pages documents from my iCloud Drive as email attachments from within Mail app? Whenever I try to add an attachment to a mail message, the iCloud Drive window pops up allowing me to browse to the required document, I then select the document but the pop up window just disappears leaving the mail message with no attachment added. Strangely, using the same method, I can add docx files, jpg's, pdf's etc (basically everything APART from Pages, Keynote and Numbers files).

Appreciate any advice - hopefully it's just something obvious that I've overlooked!

Steve