Rather than exporting a whole document out of Acrobat, I'll focus on a table within a PDF page. Suppose you'd like to have this table's data in a spreadsheet so you can manipulate it. There's no need to retype the data into Excel. All you need to do is use Acrobat's Selection tool to highlight the content you wish to export.
Mankin, David R. Blogs.com (2009). Articles>Information Design>Databases>Adobe Acrobat