If theres no way of editting form the original, or no way of recreating it easily, then you r best bet is to use the 'Touchup Text' feature / toolbar.
Although, it isnt the best tool, its ok as a last resort (it breaks the file up a bit - especially if you are passing it on as a pdf again) if you want to quickly add a couple of things its ok..
You can find it in the toolbar at:
Tools > Advanced Editing > 'Touchup Text Tool'
Again, use it as a last resort.