In Website Maker's "Objects" panel, just go to "My media" => "Uploaded" => "Other". This is the section where you can deposit basically any file type other than the photo, video and audio file types that have special meaning in the program and become layout elements of your page. Other file types will be represented by an icon upon being uploaded via the "Upload" button and inserted into the page and can be opened/downloaded by the visitors of your page later by clicking on said icon.