I'm trying to fill out a PDF form file, but I can't enter anything in the yellow fields. I've tried Ubuntu Linux with Adobe Reader 9.4.2 and Evince 3.2.1, however, I'm not sure this is a problem with the applications rather than too restricted PDF file. Can anyone help me to interpret the document properties?

Unfortunately I cannot share the PDF file due to privacy reasons, but I'm happy to try any known fillable PDF form you can link to. Thanks! :-)