TurboTax program has innate function with which users may export their tax return files (most often .tax) as PDF documents, i.e. natively achieve tax to pdf conversion. The same can most likely be also achieved with the print function in case a virtual PDF printer is installed on the computer.
Nonetheless, a lot of people are just looking for a general way to convert some generic tax form to PDF. In this case just look for a PDF export function or at least print function in a program that can work with your .tax files.