Attaching doc to email is a request on uservoice from 2011

[fardream]

Enable document attachment in emails – Feature Suggestions for Windows Phone

This uservoice thread was started almost 3 years ago - and they are still wondering why people don't buy their phones...

 

[Laura Knotek]

It is possible to attach documents to emails using the the Files app. Files | Windows Phone Apps+Games Store (United States)