How do I add a ALT TAG to a pdf document

I want explanatory text displayed when I hover over the pdf and 'save to My Documents' icons so that it is obvious what they do. I am bit of a novice to Mendix, So anybody that is able to help me could you please give me a step by step guide? Thank you Omid
1 answers

This cannot be a tooltip btw, it needs to be a class I think. As there is no toolti option on a PDF logo.

Thank you