A recipient of a mail which has action attachments can view the comment that was made while completing the action as well as the action attachments from the mail.
1) To view the comment, click on the "+more" button under "Comments" in the Actions section of the mail.
2) To view the attachments in the action, click on the Attachments icon (highlighted in red below) in the Actions section. This opens a popup which gives you the option to download the action attachments.
Access action attachments in Mailed Documents
The documents that are attached to Actions are stored in Mailed Documents on Fulcrum, which can be accessed from the Left Navigation menu. These documents have a label called "Action" under "Item Type."