Hi ,
I wonder you are using Acrobat to convert PDF'.
Please tell the Acrobat and Outlook version installed on your machine.
Also tell the OS you work on.
Try performing the same action again.
Before you proceed,please check if you Acrobat is updated to the latest patch and if you are on windows ,try to repair your Acrobat as well.
Let us know if this helps.
Regards
Sukrit Dhingra