As with all text areas in Moodle, it is possible to add attachments as a link within the text.
Do something like this:
- Type 'Download description'
- Select this text, then click on the 'link' icon in the text editor
- Select the 'Browse' icon at the end of the 'URL' box
- Select the 'Upload' repository (or a different repository if the file is stored somewhere else) and upload the file