Kanban Tool integrates well with Google Drive, Dropbox, Box and OneDrive file hosting services.
To enable the integration, go to the Settings - Power-Ups page, and enable the service you store your files on: Dropbox, Google Drive, Box or OneDrive. You can choose as many as you are using. Now you’ll be able to link file attachments from your file hosting services directly to Kanban Tool cards.
To attach a document stored in your preferred hosting service, simply click on the add attachment link, and choose Attach from Google Drive / Dropbox / Box etc. from the drop-down menu.