They are:

[chema@localhost printers]$ grep _ PDF-WRITER.xml.in
<_Name>Create a PDF document</_Name>
[chema@localhost printers]$ pwd
/home/chema/cvs/gnome2/libgnomeprint/data/printers
[chema@localhost printers]$ cd ../..
[chema@localhost libgnomeprint]$ cd po
[chema@localhost po]$ grep "PDF" es.po
#: data/printers/PDF-WRITER.xml.in.h:1
msgid "Create a PDF document"
msgstr "Crear un documento PDF"
[chema@localhost po]$

Do you not see them in your .po file or are they not getting
translated? I am unsure if the code is calling _ on them for
translation, I'll make sure it is.

A few examples are in gnome-print-paper-selector.c:

static const GPPOrientation porient[] = {
        {"R0", "Straight", {1, 0, 0, 1, 0, 0}},
        {"R90", "Rotated 90 degrees", {0, -1, 1, 0, 0, 1}},
        {"R180", "Rotated 180 degrees", {-1, 0, 0, -1, 1, 1}},
        {"R270", "Rotated 270 degrees", {0, 1, -1, 0, 1, 0}}
};

etc.

I find those examples from libgnomeprintui's code translated inside
libgnomeprint's .po, which is irritating to me. It doesn't seem to
work with the Debian packages, I'll compile a Garnome if I find the
time to check.

Behaviour is the same using garnome 0.21.2.
I tried it with French and German locales: The comboboxes of the print
dialog are not translated at all. The Items - "Straight" etc. - are
used in the cited way in libgnomeprintui without appearing in
libgnomeprintui.pot, and also appear in XML files in libgnomeprint,
where they are in libgnomeprint.pot and translated, but apparently not
used by the application itself.

Created attachment 14658 [details]
screenshot

Created attachment 14659 [details] [review]
patch, libgnomeprintui part

Created attachment 14662 [details] [review]
libgnomeprint part of patch

Fixed in CVS