Can’t open attachments in outlook app

First off I've had a look and no other threads seem to help with my question, they all seem to relate to accessing outlook through the Web.

I've just downloaded the outlook app on my new android phone, and I can't open any attachments. I've downloaded adobe reader but still no joy.

It's a pdf that I'm trying to open, they're just showing up like standard text and I'm unable to click on them.

Any help would be great.

Thanks

Danni