The package creates slides for on-screen presentations based on PDF features without manipulating TeX’s typesetting process. The presentation flow relies on PDF’s abilities to display content step by step. Features include: – Free positioning of anything anywhere in painted areas on the slide, as well as in the main textblock; – Numerous attributes to control the layout and the presentation flow, from TeX's primitive dimensions to the visibility of steps; – Feature inheritance from global to local settings, with intermediate types; – Basic drawing facilities to produce symbols, e.g., for list items or buttons; – Colors, transparency, shades, and pictures; – Navigation with links, pop-up menus, and customizable bookmarks; – Easy switch between presentation and handout; and – PDF transitions. Besides the traditional documentation, the distribution includes visual documentation and six demo presentations ranging from geometric abstraction to classic style to silly video game. Lecturer is designed to work with all formats, but presently fails with ConTeXt MkIV (because of clashes in management of PDF objects, probably), works only with pdfTeX and LuaTeX for the time being, and requires texapi and yax, both v.1.02.