I'm using the converting option from PDF to DOCX and some files come back with an "unknown error". I wasn't able to convert a 500 page PDF allthough I have tried various times. It stops at about 70% and then just hands out an error. I have used the app to convert files with similar content and had no issues. I have attached the file.
Hope you are doing well and sorry for the trouble. As described you are getting the 'Unknown Error' when exporting the PDF file to MS Word.
As mentioned its an issue with this specific PDF file, I have checked the file and found that it is created using a non Adobe application 'iLovePDF', Please try to create the PDF using Adobe Acrobat DC application and see if that works for you.