Strictly speaking, it cannot be done totally without data loss, due to the nature of PDF, as opposed to Office documents. Excel and other Office documents carry much more information: they are flexible, fluid, can be rendered to different paper sizes. Besides, they support inner structure: for example, if you have auto-numbered sections in your Words document, you can always add a new one, and the content will be automatically re-numbered, TOC updated, and a lot more stuff like that, notably, styles. Excel documents contain formulas. They are structured: they execute, not rendered on paper.
With PDF, nearly all such information is lost.
Please see my past answers:
Convert Office-Documents to PDF without interop
Question Convert word to PDF without offce or openoffice