When I try to open the PDF file I need it looks this way (I have tried Evince, Chrome and Firefox), saying
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.
For more assistance with Adobe Reader visit http://www.adobe.com/support/products/acrreader.html.
I have found an explanation saying
Certain PDF files (dynamic XFA forms) created in Adobe LiveCycle can only be opened in Adobe Reader and Adobe Acrobat. When you try to open these files in an alternative PDF viewer, then you will see this error message.
How are such files meant to be opened on Ubuntu given the official Adobe Acrobat Reader package is deprecated?
It's not a real problem for me practically as I have actually managed to install Adobe Acrobat Reader 9 (BTW I am, however, afraid this ancient version is going to start having problems with opening new files of this kind soon) on Xubuntu 15.10 a reasonably tidy way by unpacking the old Ubuntu DEB package, putting the necessary files to a subdirectory in /opt and editing the Reader's launch scripts but I believe it's a pretty serious issue for using Ubuntu in commercial/academy/government environments so there is to be a more proper way.