You need to make sure that the URL has a correct file type at the end. i.e. .pdf for PDF files and .xls (or similar) for spreadsheets. The tool will recognize most file types, but what you got above was the uninterpreted dump of the spreadsheet.If you were a computer you could have read it.
Word documents stored in Google docs should also work, but Google docs does not necessarily put the file type in since it does not need it.
You should also be able to handle presentations that are in Google docs the same way. I may have time to explore the range of documents available but I think that any you can see in Google Docs will work as long as the URL includes the file type at the end.