You can upload any file format that dtSearch supports, see the link below.

https://support.dtsearch.com/faq/dts0103.htm

If you intend to have Filters or Facets  the file format must support dtSearch Automatically-detected fields. 

PDF or Microsoft Word are recommended. PDF is preferred if you want to automate your publishing process.

Whether you are using the Search Cloud One API, or the Search Cloud One WordPress Plugin, before uploading a large batch of files, it’s very important  to carry out pre-publish checks.

After the pre-publish checks, upload a  small trial batch. Make sure your search page, results and documents can be searched, found and displayed correctly.

Once uploaded, you can only delete individual files; it will be time consuming and costly to edit or replace hundreds of files.  If you delete the index, you will have to create a new index, fields, and your search category and shortcode in the WordPress Plugin again.