You can embed a PDF file into a cell of an Excel worksheet and then use Excel's security features to lock the object. This allows you to take advantage of both technologies.

If the viewer does not have Excel installed on his computer, the file will open in another application that supports the file format in which you save the spreadsheet.

Microsoft Word can accommodate a surprising number of file formats, and even take in Excel and PowerPoint data, though it might look funny. Here's how.