I assume you get the conversion error, while converting the document online via web browser https://cloud.acrobat.com/exportpdf or is it through the desktop application Adobe Reader DC?
You may refer to the related thread for the similar discussion- Conversion Failure and follow the troubleshooting steps suggested.
Let us know if the solution provided doesn't help you.
I'm trying through desktop application Adobe Reader DC without any success?
I apologize for the delay in response.
The conversion failure issue should have now been resolved. However, if you are still experiencing the same problem then you may share the exact version of Adobe Reader. Open Adobe Reader>Help>about Adobe Reader
You may try installing the latest patch- Release Notes | Adobe Acrobat, Reader and see if this helps.
If you have managed to find the solution, then please share your findings.