Attachments are a great way to include PDFs and other files with your newsletter. They appear as a downloadable link, so save screen real estate in your newsletter and allow relevant readers to download and consume the attached file.
To insert an attachment
Click inside the article where you'd like the attachment to appear
To the left of the flashing cursor will be a grey '+' button - click this
From the menu that appears, click Attachment
The file picker popup will appear. Choose an already uploaded file by single clicking it, or upload a new one
Once a file has been selected, press the Insert button
To delete an attachment
Find the attachment on the page you wish to delete
Click to select it, and press backspace on your keyboard