Changing the font size of text in the page will only affect the current page, but there are also options to change the font sizing in the template and also the font family as well.
You can visually change the structure of your website by using Headings to separate content.
Pages should have only one H1 heading (as set in the page options) H2, H3, H4 can be used as warranted by the content.
Examples of the different text formats used by this website
You can increase the size of any text on the page, either by selecting the required text area via click and drag, or by clicking into the text itself which will change the the entire paragraph or heading.
Drag-drop and Contentbox also give you the options to change the font-weight, line-height and letter spacing elements of the text in the same window.
You can also change the font sizing in the template, this will affect all of the elements found on the website, via the
DESIGN > Colours, Fonts and Styling > Custom Style Elements section.
There are a lot of options on the Custom Style Elements page, you will need to scroll down to the TEXT LINKS AND BUTTONS section.
You can also affect Product List page elements in the Custom Style Elements area - look for the Product Lists / Galleries / Blog Lists section.
In the Drag-drop and Contentbox editors you can select text and choose a different font only for the current element/page.
To change fonts site-wide, set your Heading and Body fonts via the DESIGN > FONTS AND TEXT COLOURS area.