I.R.I.S. Readiris 14 for Mac User Guide - Manual (Page 106)

Readiris TM 14 – User Guide
101
Resolution
Readiris retains the original resolution by default.
You can also choose to reduce the resolution to a lower dpi
(between 50 and 300).
Note that you cannot increase the resolution.
P
AGE
S
IZE
In Readiris the page size of the documents you scan and open does
not necessarily have to be the same as the page size of your output
documents.
When generating DOCX, XLSX, ODT or RTF documents, you can
select the preferred page sizes: