I.R.I.S. Readiris 14 for Windows User Guide - Manual (Page 116)

Readiris TM 14 – User Guide
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
Select the desired PDF type from the drop-down list:

PDF Image-Text (= PDF Searchable Image). This file type is
most commonly used. It contains two layers: the recognized text,
and the original image on top of the text. This way, you have
both access to the recognized text and you still see the original
image.
Note: since the image covers the text, any recognition mistakes will
not be visible.

PDF Text-Image. This file type is the opposite of PDF Image-
Text. It contains the original image in the background, and the
recognized text on top of the image.
Note: any recognition mistakes will be visible in this format.

PDF Text. This file type contains the recognized text, but does
not contain the original image of your document. Any images in
the original document are included as graphics in the PDF file.