Having 4-way OCR enabled doesn't create any hits for text that reads in non left-to-right direction in some documents.
Document(s) have layout, structure, or fonts that are difficult to OCR.
To increase the OCR success rate for such documents, modify the value of the 'OCRPredefinedProfile' key in the 'ZyLAB.EDiscovery.Processors.TiffProducer.dll.xml' file typically located in the '\Program Files (x86)\ZyLAB\EDiscovery\Ediscoveryservice\Assemblies\Performers\ZyLAB.EDiscovery.Processors.TiffProducer' folder.
<setting key="OCRPredefinedProfile" value="DocumentArchiving_Accuracy" />
Note: The default value for this key is 'Default'.