I.R.I.S. IRIScompressor Pro Mac - Manual (Page 21)

Using IRISCompressor Pro
22

Select Create one file per file in case you want to generate a
separate output file for each input file.

Select Create one file per batch in case you want to combine all
your input files in one single output file.
Note: IRISCompressor can process a maximum of 25 pages at a
time. So, make sure the total number of pages contained in your
different files does not exceed 25. For your information: 1 image
corresponds to 1 page. If you try to compress documents that
contain more than 25 pages, only the first 25 will be processed.
Note: the settings you select in the IRISCompressor Options
menu are saved automatically. Next time you use IRISCompressor
by right-clicking a file it will apply the same settings.