When merging ps files, some pages are missing

Yes, .ps means postscript. We are using the below method to distill the .ps to pdf

FOR EXAMPLE

%!
% PostScript program for distilling and combining multiple PostScript files.
% When embedding font subsets, it is highly recommended you use this technique
% to distill multiple PS files so only one font subset is used for each font.

/prun { /mysave save def       % Performs a save before running the PS file
        dup = flush            % Shows name of PS file being run
        RunFile                % Calls built in Distiller procedure
        clear cleardictstack   % Cleans up after PS file
        mysave restore         % Restores save level
} def

(d:/PS-Merge/3376815/9781107039322_pod.ps) prun
(d:/PS-Merge/PS-Merge/3376815/9781107039322c01.ps) prun
(d:/PS-Merge/PS-Merge/3376815/9781107039322c02.ps) prun
(d:/PS-Merge/3376815/9781107039322c03.ps) prun
(d:/PS-Merge/3376815/9781107039322c04.ps) prun
(d:/PS-Merge/3376815/9781107039322c05.ps) prun
(d:/PS-Merge/3376815/9781107039322c06.ps) prun

% INSTRUCTIONS
%
% 1. Locate all PostScript files to be distilled.
%
% 2. Make a copy of this file and give it the name you want to have as the prefix
%    for the resulting file. For example, you could name this file MyBook.ps.
%
% 3. Include a line for each PostScript file to be run using the pathname syntax
%    appropriate for the platform running Acrobat Distiller.
%
%       Macintosh pathname syntax:  (Macintosh HD:Folder:File.ps) prun
%       Windows pathname syntax:    (c:/mydir/file.ps) prun
%       UNIX pathname syntax:       (./mydir/File.ps) prun
%
%       Note: The syntax for Windows may look strange, but double escaping the
%             backslash character is required when using filenameforall.
%
% 4. Distill the file on the machine running Acrobat Distiller.