We’re sorry to hear this, as per the description when you convert a Word document to PDF, you are getting an error message "Error 400", Is that correct?
The record shows that you are subscribed to Adobe PDFPack services with your current Adobe ID, try converting the Word file to PDF using the URL https://cloud.acrobat.com/convertpdf with your Adobe ID and password on a browser like Chrome, or Firefox, or Safari and see if this brings any difference.
If you are using the freeware Adobe Reader to convert the Word file to PDF and getting the error message, please sign out and sign back in Adobe Reader using your current Adobe ID and check for any pending updates of Adobe Reader from help>check for updates, reboot the machine after updating Reader and try converting the Word document.
For more troubleshooting, you can refer to Adobe article Troubleshooting Create PDF, Export PDF, Adobe Send, Fill & Sign … services(PDFPack or Document Cloud...
Let us know how it goes and share your findings.
[Moved the thread from Creating PDF to Document Cloud services]