As per the issue description, the Save option is greyed out in Acrobat Pro DC, Is that correct?
If the "Save" option is out, then please try the following troubleshooting steps:
If the issue still persists, then please remove the Acrobat Pro and reinstall it. Assuming you are using a Windows machine, remove the Acrobat using Adobe Cleaner tool: Download Adobe Reader and Acrobat Cleaner Tool - Adobe Labs Link: http://labs.adobe.com/downloads/acrobatcleaner.html
Restart your computer and install the Acrobat Pro dc from Download Pro or Standard versions of Acrobat DC, 2017, XI, or X Link: https://helpx.adobe.com/acrobat/kb/acrobat-downloads.html
If the "Save As" option is greyed out, then please try the troubleshooting steps:
Hope this helps, and keep us posted with the results.