The following is from pkgsrc patches to fix problem with interactive forms:
(This is not my writeup or patch.)

-if a choice field defines both an "export value" and a "name", use the
 latter as "value" if selected (according to the PDF spec) -- makes
 that I can fill in my company's travel expenses form correctly
 (there is still an issue with captions of check boxes / radio
 buttons which looks like a font problem)

$NetBSD: patch-al,v 1.3 2009/04/06 09:29:27 drochner Exp $

--- poppler/Form.cc.orig	2009-01-28 22:56:21.000000000 +0100
+++ poppler/Form.cc
@@ -546,7 +546,7 @@ void FormWidgetChoice::_updateV ()
     } else if (numSelected == 1) {
       for(int i=0; i<parent->getNumChoices(); i++) {
         if (parent->isSelected(i)) {
-          obj1.initString(new GooString(parent->getExportVal(i)));
+          obj1.initString(new GooString(parent->getChoice(i)));
           break;
         }
       }
@@ -555,7 +555,7 @@ void FormWidgetChoice::_updateV ()
       for(int i=0; i<parent->getNumChoices(); i++) {
         if (parent->isSelected(i)) {
           Object obj2;
-          obj2.initString(new GooString(parent->getExportVal(i)));
+          obj2.initString(new GooString(parent->getChoice(i)));
           obj1.arrayAdd(&obj2);
         }
       }