Almost every tax preparation and accounting software nowadays has default PDF export function, so it should be not hard to export .t15 tax return files as .pdf documents, i.e. achieve t15 to pdf conversion. Just keep in mind that exporting to PDF is usually done only for viewing or printing purposes.
In most cases, .t15 file contains tax return form prepared using the H&R Block Tax Software 2015 and it is this or later version that is needed to successfully export t15 to pdf.
Updated: December 9, 2016