Unable to extract text form pdf

Hi, I am using adobe api to extract text from pdfs, and for some pdf I am getting error from the api saying "Unable to extract content. Internal error". The detailed error message is as follows:

error_code=oex.error_code,
adobe.pdfservices.operation.exception.exceptions.ServiceApiException: description =ERROR - Unable to extract content. Internal error; requestTrackingId=MFzu5ApezIaRy8SG6xa58WdCHlsmNXyW; statusCode=500; errorCode=ERROR

If someone could help me understand this issue, it would be really helpful. 
Thanks.