When using markdown code blocks the resulting monospace font size is too large in DOCX documents.
I can adjust the font size of paragraphs by specifying a custom
Pandoc, when creating DOCX (MS Word) documents uses a reference.docx file. This has to be given on the Pandoc command line. Pandoc will then extract all default styles and formatting settings (unless they use custom names) from this reference DOCX and apply them on the generated DOCX:
pandoc -t docx -o out.docx in-markdown.txt --reference-docx=my.docx
The best way to arrive at a Pandoc-usable reference DOCX is to generate a first simple DOCX with the help of Pandoc, then take it to a Word installation, open it and change the styles to be used by you to your liking. Then save it, take it back to Pandoc and use it as a reference.
For ODT (LibreOffice/OpenOffice/OpenDocument) in addition to the reference.odt (which you can use with the --reference-odt flag), there's also a template. You can print the default template with pandoc -D odt, then modify it and use it with pandoc -o out.odt --template=modifiedTemplate.odt
Last advice: use the latest Pandoc version! (Current is 1.13.2.1. For end of this month a 1.14 is expected.) Its DOCX support improved considerably in recent releases.