From Adobe's site:

"You can also export a PDF to plain text or accessible text. Accessible text follows the reading order preference selected in the Reading preferences, and includes comments and form fields in its output. Accessible text also includes some formatting, such as line breaks. Any alternate text in the document tags is used in place of images and figures. Plain text follows the structure order of text in the document and ignores all artifacts and figure elements in the conversion. Hard hyphens are preserved, and soft hyphens are removed."