When it comes to combining multiple files into a single PDF, FineReader can process the task for a long time because by default some processing options are enabled.

The following settings will allow you to combine files faster

1. Disable changing image quality, resolution and compression as below:
   
   If PDF files you need to combine are searchable, then select in Full-text search: As in original document.
2. Disable all Image preprocessing options:
   

If you still face some issues, please contact Support Team by submitting a request.