is there any workaround
"not being able to use Outlook's other windows while outlook Draft message window is active (launched through Send File as attachment)."
This is a known issue.
Works great with Thunderbird but not with Outlook.
It seems to be some issue with the Outlook email account in Adobe Reader.
Have you tried deleting & adding the outlook account again in Adobe Reader?
Open Adobe Reader, navigate to Edit menu -> Email Account -> Remove & add outlook email account again.
Let me know how it goes.