The most obvious choice for indt to pdf conversion is to use Adobe InDesign or some other professional document preparation software with InDesign format support to export your .indt templates files to PDF. Just keep in mind that templates may not contain the full document, just the general layout.
However most users deal with the problem how to convert .indt templates as PDFs without Adobe InDesign. Sadly, there probably is no good program for Windows that would allow this, although some users reported that you could export .indt files to PDF directly from your Adobe Creative Cloud account which you can create for free. But this option may have been removed in previous year.
Mac users also have an option with Art View program, which is an app that supports viewing (and possibly printing to PDF) of various Creative Cloud documents, including .indd documents from Adobe InDesign.Open INDT file Open PDF file
Professional desktop document publishing software from Adobe
Mac version od Adobe's popular document designing and publishing software