如何使用 .cls 文件增加边距

Question

抱歉，这是一个简单的问题（对于 Latex 来说相对较新！），但是我对这个试图理解的预先完成的 .cls 文件感到有点困惑。

我正在尝试减少 A4 文档的边距，因为目前间隙很大，想知道是否有人可以说明我可以/应该进行哪些更改？

\newcommand{\bookclass}{book}

% Font size, this option is passed to book class. T.G. : use regular, 10- to 12-
% point size for text. Default is 12pt.
\newcommand{\@ftsize}{}
\DeclareOption{10pt}{\renewcommand{\@ftsize}{10pt}}
\DeclareOption{11pt}{\renewcommand{\@ftsize}{11pt}}
\DeclareOption{12pt}{\renewcommand{\@ftsize}{12pt}}

% Left side margin. 
% [1.5in], [1.7in]
% T.G. : the left margin must be at least 1.5 inches (recommend 1.7). default is
% 1.7, unless [1.5in] is specified.
\newcommand{\@lmarwidth}{}
\newcommand{\@smarwidth}{}
\newcommand{\@texwidth}{}

\DeclareOption{1.5in}{%
  \renewcommand{\@lmarwidth}{.5in}%
  \renewcommand{\@smarwidth}{.0in}%
  \renewcommand{\@texwidth}{6.0in}%
}
\DeclareOption{1.7in}{%
  \renewcommand{\@lmarwidth}{.7in}%
  \renewcommand{\@smarwidth}{.0in}%
  \renewcommand{\@texwidth}{5.8in}%
}

% One and half or double spacing?
% [onehalf], [double]
% T.G. : use either double or 1.5 line spacing for the body of text. default is
% double, unless [onehalf] is specified.
\newcommand{\@spacing}{}
\DeclareOption{onehalf}{\renewcommand{\@spacing}{\onehalfspacing}}
\DeclareOption{double}{\renewcommand{\@spacing}{\doublespacing}}
\AtEndOfClass{\@spacing}

% Draft or final version?
% [preprint], [submission]
% Default is submission.
\newif\if@preprint

\DeclareOption{preprint}{\@preprinttrue}
\DeclareOption{submission}{\@preprintfalse}

% [seploa]
\newif\if@seploa
\@seploafalse
\DeclareOption{seploa}{\@seploatrue}

% Other options are passed to the book class.
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{\bookclass}}

% These are the default options.
\ExecuteOptions{12pt,1.7in,double,submission}
\ProcessOptions\relax

\if@preprint
\PassOptionsToClass{twoside,openright}{\bookclass}
\else
\PassOptionsToClass{oneside,openany}{\bookclass}
\fi

\PassOptionsToClass{\@ftsize}{\bookclass}

\LoadClass[letterpaper,onecolumn]{\bookclass}

% -------------------------------------------------------------------------------
% Set up page layout.

% \evensidemargin is used when [twoside] is set (by [preprint]).
\setlength{\oddsidemargin}{25pt}
\setlength{\evensidemargin}{25pt}
\setlength{\textwidth}{\@texwidth}
% Other margins. T.G.: all other margins must be at least 1 inch.
\setlength{\topmargin}{0in}
\setlength{\headheight}{.5in}
\setlength{\headsep}{0.3in}
\setlength{\footskip}{.5in}

先感谢您，