Hi Chaitanya,
I did not try this before. But in adobe, before, I tried, created a button called 'Save As', Script of that button was calling a menu function, like
app.execMenuItem("SaveAs");
http://acrobatusers.com/tutorials/creating-save-button-livecycle-designer
Probably you could create a button in your form called 'Read out Loud' and write similar code. Not sure, if it works. Just sharing my idea.
Thanks,
Rakesh