How can I send files from Trello Cards to One Drive?

[Eric Powell]

Is it possible to create bidirectional integrations between Trello and One Drive? 

I want to be able to send Word, PDF, Excel files from Trello cards to One Drive. 

[Theodoro Reato]

Hi Eric,
Once you attach the file, you can open and it will open in OneDrive, then you can make the changes and it is changing the original file.
There is no two-way integration as it is the same file. You should be fine to use it as you wish.