If you already have an ebook writing and PDF production workflow that you're happy with, you can upload a PDF directly using our Bring Your Own Book feature. This includes PDFs generated using LaTeX, or even those saved from Word.
With Bring Your Own Book, you only need to upload at least one of PDF,
EPUB and MOBI. PDF-only is totally fine, especially if you're writing a computer programming book: PDF is still the dominant format for computer programming books. (If you were writing a novel, we'd strongly recommend uploading EPUB and MOBI as well: EPUB for phones, and MOBI for Kindles.)
If you already write in LaTeX and are happy with your workflow, the Bring Your Own Book option is definitely the best option.
If you already write in Microsoft Word, you can either upload the Word document and see if our ebook generators can handle it, or you can upload a PDF directly using the Bring Your Own Book option. The reason we support Word, and the supported formatting for Word documents, is explained further here: https://leanpub.com/blog/2016/03/writing-leanpub-books-in-word
Finally, note that we generate our own PDFs using LaTeX that we've produced from Markdown or Markua. Leanpub depends on LaTeX.