Ask HN: What's the best tool to convert any doc to PDF?

I am working on a side project that needs to convert any document (typically word/excel/text) to PDF that can be rendered on the server via pdf.js

I see lot of cloud SaaS products that seem to do it - but I don't know how good of a quality they provide. What's the best open source tool that can handle this ? I would consider commercial product also as a fall back. Appreciate pointers.