By tapping the "View Documents" button on the actions menu whilst on the authorisations detail page. You will be shown the documents page, this will have a list of all documents applied to this work order.

At the top of a list, is show / hide related documents button, by tapping this you will show / hide all documents that are related to this type of work order.
To view a certificate/document from the list simply tap on the name or the "View" button at the end of the row.