I scan my documents, they become a PDF, when I try to convert to word or excel I receive a "conversion failure" message. Only once have I been able to successfully convert a document.
Where exactly you are getting the error message? Is it online via web browser https://cloud.acrobat.com/exportpdf or using desktop application Adobe Reader DC?
If you are getting error online then you may use the desktop application Adobe Reader DC https://cloud.acrobat.com/exportpdf and let us know if this makes any difference.
Also, you may check with a different web browser or if you are using any internet security software then turn it off for a while.
[Antivirus software can help protect your computer against viruses and other security threats. In most cases, you shouldn't disable your antivirus software. If you have to temporarily disable it to install or activate other software, you should re-enable it as soon as you're done.]
I think I figured it out - I was trying to convert while in the free adobe reader screen - once I logged into adobe, I had no problem at all.
Glad it worked for you. And thanks for sharing your findings.