The Screen Reader works using a parameter based on CSS selectors to match the text to resize and to apply dyslexic font family in the current page, so that this can be adapted and applied to every Joomla template.

The Screen Reader ships with a preconfigured set of CSS selectors to match the most common Joomla templates, but if this doesn't suit with your template you can add or replace specific CSS selector to match the text part of your template that you want to be resized.
A precious tool to identify the HTML structure and the CSS selectors to use in this process, is the Chrome developers tool or Firebug for Firefox to inspect easily how your template is formatting elements.