/usr/share/texlive/texmf-dist/dvipdfmx/dvipdfmx-paper.cfg is in texlive-base 2013.20140215-1ubuntu0.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 | %% PDF Document Settings
%%
%% Papersize Option:
%%
%% p papersize-spec
%%
%% papersize-spec is 'paper-format' or length-pair, e.g., 'a4', 'letter',
%% '20cm,30cm'. Recognized unit is 'cm', 'mm', 'bp', 'pt', 'in'.
p a4
|