Task > What tab: click on the “Add an attachment” button and select your document.
After being uploaded, the attachment will appear at the bottom of the task details panel.
In the What view, when a task contains an attachment, an icon is displayed.
Note1: An attachment can not exceed 100 MB, but you can add as many attachments as you want.
Note 2: The addition of attachments is reserved for users with a subscription. However, users with a Free count can download attachments.