How to set several recognition languages?
Call SetPredefinedTextLanguage method with a parameter which contains several language names separated with commas, for example, "English,French,German".
DocumentProcessingParams.PageProcessingParams.RecognizerParams.SetPredefinedTextLanguage("English, French, German");
For some language combinations, there are separate language names. For example, “Mixed” language name corresponds to Russian and English languages.
All language names can be found in "Help" → "Specifications" → "Predefined languages".