I use Markdown to write my stories, and have started using Pandoc to convert to PDFs and HTML. The PDFs could use improvement, however, and I would like to make them look like Manuscript submissions.
bookdown would be a simple, easy way to write books in Markdown.
For a start, one can follow the tutorial itself to make a authentic looking manuscript.
Here are the directions to develop templates: https://bookdown.org/yihui/bookdown/templates.html