I.R.I.S. Readiris 14 for Windows User Guide - Manual (Page 140)

Readiris TM 14 – User Guide
147
Note: in Readiris Pro the number of pages you can process inside a
single project is limited to 50.
Scanning multiple documents on a flatbed scanner

Click the down arrow beneath the Scan button to access the
Scanner Settings.

In the Scanner Settings windows, select Scan another page
after and then indicate after how many seconds the next page
must be scanned.
This way, you avoid having to go back to your computer and
click the Scan button inside Readiris. You can simply replace the
pages at your own pace and Readiris starts scanning the next
page automatically.