I installed the current version of FoxIt reader (for “64-bit Linux”) on Debian 10.3 64-bit. When I open the “512-927_fillable.pdf” file with it, I get the “Please Wait…” message:
If this message is not eventually replaced by the proper contents of the document, your PDF viewer may not be able to display this type of document.
You can upgrade to the latest version of Adobe Reader for Windows®, Mac, or Linux® by visiting http://www.adobe.com/products/acrobat/readstep2.html.
Of course, I get the same message with the distribution-provided tools “xpdf” or “evince”.
However, in my case, I also have access to a computer that dual-boots Linux and Windows Enterprise 7 (out of support), and on the Windows partition we have Adobe Reader IX Pro installed (also out of support). (In fact, that’s the computer that my Life Scout son primarily uses). I was able to open the workbook in Reader, print it using the “CutePDF” driver, and create a PDF/A version of the workbook. (Except it seems to be black-and-white rather than color; but the text s all there.) Here’s the result, in case it helps anyone. 512-927_flattened.pdf (892.2 KB)