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

-where iconv() is called to fill in a text field, use "UTF-8" and
 "UTF-16BE" as encoding names rather than the less portable
 "UTF8" and "UTF16BE" -- this makes it work on NetBSD

Not that wikipedia is always the best source, but 
http://en.wikipedia.org/wiki/UTF-8 says "... descriptions that omit the hyphen ... such as "utf8" ... [is] incorrect and should be avoided."

$NetBSD: patch-am,v 1.1 2009/04/06 09:29:27 drochner Exp $

--- glib/poppler-form-field.cc.orig	2008-10-09 22:30:34.000000000 +0200
+++ glib/poppler-form-field.cc
@@ -279,7 +279,7 @@ poppler_form_field_text_set_text (Popple
 	
   g_return_if_fail (field->widget->getType () == formText);
 
-  tmp = text ? g_convert (text, -1, "UTF16BE", "UTF8", NULL, &length, NULL) : NULL;
+  tmp = text ? g_convert (text, -1, "UTF-16BE", "UTF-8", NULL, &length, NULL) : NULL;
   goo_tmp = new GooString (tmp, length);
   g_free (tmp);
   static_cast<FormWidgetText*>(field->widget)->setContent (goo_tmp);
@@ -552,7 +552,7 @@ poppler_form_field_choice_set_text (Popp
 
   g_return_if_fail (field->widget->getType () == formChoice);
 
-  tmp = text ? g_convert (text, -1, "UTF16BE", "UTF8", NULL, &length, NULL) : NULL;
+  tmp = text ? g_convert (text, -1, "UTF-16BE", "UTF-8", NULL, &length, NULL) : NULL;
   goo_tmp = new GooString (tmp, length);
   g_free (tmp);
   static_cast<FormWidgetChoice*>(field->widget)->setEditChoice (goo_tmp);