How to make Adobe Reader default PDF viewer in Android Mail

[Domo]

Unnecessary rant.

Spoiler

Having failed to persuade my other half to get an iPhone, her Galaxy S4 Mini has arrived this morning and I'm trying to configure it. I can't believe people choose Android over IOS/Apple. With an Apple phone you take it out of the box, switch it on and after adding some mail account info you're ready to go. But this thing - oh my god. I'm losing the will.

Anyway, cut to the chase..

The question.

I've added her Yahoo email account details and sure enough messages are getting delivered. However, when tapping on a PDF attachment the 2 options I'm presented with are Chrome or Internet even though I've installed Adobe Reader.

How can I make Adobe Reader the default app for opening PDFs in Mail?

 

[Domo]

Ah - OK will try the Gmail app. Thought that might be exclusive for Google mail accounts.
In answer to your other questions, it's a Galaxy S4 Mini and the mail map we're attempting to configure is called Mail. She does get prompted which app to use when tapping the PDF attachment but the only options presented are Chrome or Internet - with the sub options 'use once' or 'always use'.

Thanks + will let you know how it goes