One option you might consider is using Markdown-formatted text files as your base. Markdown offers enough formatting tools for the job, and you can use convertors such as Pandoc at any moment to convert the file into PDF, MS Word, ODS, or another of many supported formats when necessary.

One option you might consider is using Markdown-formatted text files as your base. Markdown offers enough formatting tools for the job, and you can use convertors such as Pandoc at any moment to convert the file into PDF, MS Word, ODS, or another of many supported formats as desired, before sending it out.