Thanks for your inputs Poet. I too found out that my office subscription include Skype, however I had installed Skype separately and just now merged with my Microsoft office account. But doing this didn’t change the functionality of Skype and it still doesn’t provide attachment option for documents or some other files.
In my android smart phone, it works pretty smooth, by clicking share on any particular file, where Skype appears as an option along with other options such as messaging, whatsapp, messenger etc. However on iOS the direct sharing of file too didn’t show Skype as an available option.
Just some more exploration lead to the information that as per version history of Skype on App Store, the version was updated 4 months ago, much before iOS 11 rolled out. I think Skype is not yet optimised for iOS 11.x
Atindra