There are 2 ways to increase font size for Printable Version of Customer View:
1) Print from the customer (or order tab) and limit the # of columns (see “customize this view“) to only the required information. Fewer columns = Larger font.
2) Use ‘Export to Excel’ and you can edit column/row/text size directly from Excel.
See the video below to see how to make your text/columns bigger before printing from excel