How to attach files to emails on iPhone running iOS 8?
Documents by Readdle lets you send any arbitrary file over email. Select the file in Documents, tap Actions, then Mail to. This composes a new email with the file attached.

Upgrade to iOS 9 and you can attach arbitrary files from Apple's mail client. Documents can export files to iCloud drive for easy attachment or you can just save the file to iCloud drive from the get go and skip the Documents unless it ads value to your workflow.