In Systemsettings choose Locale -> Country/Region & Language.
Other tab -> Page Size:
kdebase/kde-runtime/kcontrol/locale/kcmlocale.cpp has two lines with:
m_ui->m_comboPageSize->addItem( ki18nc("Page size", "A4").toString( m_kcmLocale ),
From looking at the source code, this is intended. The two most used options (A4, US Letter) are replicated at the top for faster access.
Git commit 8a29700006073296923a50600ac94813c7243e42 by Christoph Feck.
Committed on 15/02/2013 at 14:00.
Pushed by cfeck into branch 'KDE/4.10'.
Insert a separator after two most used page sizes
This visually groups those to better explain why they
are duplicated in the list of page sizes below
M +2 -0 kcontrol/locale/kcmlocale.cpp