Considering PDF export function is de facto standard nowadays, almost every tax preparation and accounting software has it.
This means that it should be not hard to export .t16 tax return files as .pdf documents, i.e. achieve t6 to pdf conversion. Just keep in mind that exporting to PDF is usually done only for viewing or printing purposes.
In most cases, .t16 file contains tax return form prepared using the H&R Block Tax Software 2016 and it is this or later version that is needed to successfully export t16 to pdf. Some 3rd party alternatives Quicken / TurboTax also supposedly have support for H&R Block files.