Go to:

Admin > Mailing Lists > Send Emails

Complete all the following fields:

• Schedule send option
• Mailing List
• Content Type 
• Article
• Attachment file
  

In the Attachment File option you can select the document you would like to attach to the Mail out.

Note: The document needs to be uploaded to the Base Folder for you to select it.

You can view the post "How to upload documents to your website"
http://www.elcom.com.au/Community/forums/p/72/95.aspx

Once you have attached the file click on "Send".