Almost every modern tax preparation and accounting software has default PDF export function as standard function, so it shouldn't be difficult to export older .t13 tax return files as .pdf documents, i.e. achieve t13 to pdf conversion. Just keep in mind that exporting to PDF is usually done only for viewing or printing purposes.
Any version of H&R Block Tax Software above 2013 should have all you need to convert t13 to pdf. Some third party tax preparation tools may also support H&R Block files and allow import of historic data.Open T13 file Open PDF file
A tax preparation software
A Mac version of popular tax software