By default FineReader 15 uses N-1 processor cores available for recognition. One core is used for the user interface. When the program is launched, N-1 background executor processes (FineExec.exe) are being started. Larger amount of cores leads to larger number of pages being recognized at the same time. Therefore, multipage document recognition speed is being increased.
You can choose number of cores used for recognition in the options section Tools > Options > Other > Number of processor cores to use for OCR. Restart is required after this option is changed.
The amount of FineExec.exe processes running in the Task Manager corresponds to the number of processor cores used for recognition. The processes may remain in the Task Manager list for a short time after the program has been closed.