I.R.I.S. Readiris 14 for Windows User Guide - Manual (Page 113)

Section 9: Saving Documents
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P
APER
S
IZE
The Paper Size options allow you to define in which paper size
(e.g. A4, Letter, Legal) your output documents will be generated.
These options are available for most RTF output formats.

Click the Paper size tab and use the arrow buttons to apply and
exclude paper sizes.

Readiris will go through the active paper sizes in the user-set
order and will use the first paper size that is sufficiently large to
hold the scanned document.
Note: the default paper sizes vary depending on your operating
system.
P
ICTURES
The Pictures Options determine how the images will be presented
in the output documents, e.g. in black-and-white or in color. They
also define their resolution.