You cannot embed files such as Excel, PowerPoint, or PDF directly into manuals, regardless of the file type or application they originated from.
However, you can register online files that start with "http" or "https" as external links.
Reference: Add link to manual (Web Browser)
https://teachme.jp/8/manuals/8733762
When registering files as links to manuals, online storage (online data storage service) can be convenient. By uploading files to online storage, you can obtain a URL to access the files. Note that online storage and other third-party tools are not covered by our support.