When you buy a license for the History fonts, you automatically get access to the online layering application History Remixer. You need to be logged in to your account to use History Remixer to generate PDF files.
History Remixer allows you to control the type layers and text separately. It doesn't, however, allow finer typographic control such as adjusting the tracking, kerning, individual character colour, etc. If you need these finer controls, you should first install the History fonts on your computer, then make a PDF file in History Remixer, and edit the PDF in Adobe Illustrator®.