Ah, but if it has form fields, it is a form. They are a radically different kind of thing to the other kind of content on the page.
Sorry, I don't know what that means to the tool or accessibilty, but I thought it useful to make it clear that a form is a form whether you can type on it or not...
You cannot add alternate text with TORU.
No you cannot add alt text with the Touch-Up Reading Order tool (TURO?).
Acrobat considers Buttons a Form control.You need to add a Tooltip for the Button using the Forms Panel.
Is this button one that was created with the Form Tool or is it a Flash or Java button? These instructions only apply to a button created using the Form Panel. If the object is Flash or other multimedia you will have to address this another way, depening on how the document was created.
I was trying to find an Adobe link that shows you how to do this, but I don't see this issue addressed in their videos. Still they are useful and you may want to check them out -- http://tv.adobe.com/show/accessibility-adobe/
To add the "Tool Tip" --
Open the Form Panel, click "Edit" and select NO if a popup reads "Currenty there are no fields... let it scan your document for what it thinks are fields. ..." Just Say "No".
Once the Form Editor is running you select your button, right click and add a "Tool Tip" in the general tab. That is the equivalent of alternative text for Form Fields and Buttons.
If these instructions do not work it would suggest that your button is NOT a Form Control and perhaps was added using Flash.
Good luck and let us know how you resolved the problem.
This document may be useful to you.
--| Creating accessible PDF forms and Interactive Documents with Acrobat X Pro
Acrobat accessibility training resources