Once converted to outlines in a drawing program, you can alter the shapes of letterforms to produce a customized piece of typography, such as a logo. But you can’t alter the fonts themselves, or use them to make new fonts, nor engage anyone to do this for you. Such adjustments are considered “derivative works” under United States law, and they require the prior written permission of Hoefler & Co. as their copyright holder. You’ll find this described in greater detail in your End-User License Agreement.
If you need an Hoefler & Co. font to be extended to include additional functionality, please contact our sales office for further information.