This is going to sound like I'm trolling you, but pdf.js only supports PDFs. You'll need to convert those other doc types to PDFs before using them with pdf.js.
Can you recommend any tools for this? LibreOffice butchers XLS files.
You can try MS office. If you dont want to buy/install it you can just use the in browser version. All you need is a MS account and you can also export the files as pdf..