This book is a follow-on from the previous two books in the series ("LaTeX for Complete Novices" and "Using LaTeX to Write a PhD Thesis"). It covers more advanced topics, such as iteration, expansion, command definitions and assignments (using TeX primitives or tools provided by the etoolbox package), writing class files and packages, and fetching data from external sources (CSV, XLS, ODS or MySQL). The topics covered are all aimed towards the types of documents required in administrative work, such as writing correspondence (including mail merging), invoices, curricula vitae, memos, minutes, presentations, assignments and examinations, leaflets and flyers. Document collaboration is also discussed and two popular online LaTeX editors, Overleaf and ShareLaTeX, are compared.