You can upload supplemental files as part of your Inbox messages.
Note: Attachments appear in your user files in the Conversation Attachments folder and count against the files limit for your account.
Select Multiple Files
You can upload additional files by clicking the paperclip icon again. If you accidentally select the wrong file, press the Delete icon  to remove it, or click the paperclip icon or double click the file to select a different file. When you are finished, click the Send button .