Does this produce the result you are looking for?
\documentclass[a4paper,12pt,titlepage,oneside,final]{book}
\usepackage{fancyhdr}
\fancyhf{}
\renewcommand{\headrulewidth}{0pt}
\fancyhf[cf]{\thepage}
\pagestyle{fancy}
\begin{document}
\frontmatter
\begin{titlepage}
{\bf Titlepage}\thispagestyle{empty}
\end{titlepage}
\pagenumbering{roman}
\stepcounter{page}% comment if the titlepage should not be counted
\newpage
\thispagestyle{empty}
{\bf included pdf}
\newpage
{\bf declaration}
\newpage
{\bf Acknowledgement}
\newpage
\thispagestyle{empty}
{\bf included pdf}
\tableofcontents
\mainmatter
\chapter*{introduction}
\pagenumbering{arabic}
\addcontentsline{toc}{chapter}{introduction}
\chapter{1st chapter}
\end{document}
This omits the number on the title page and included pdfs but counts them. (Comment the relevant line if you don't want to count the title page.)

EDIT: This does leave one problem which is not to do with the page numbering of the pages as such but, rather, with the way they are designated in a PDF viewer. Although the page shows 'iii', for example, the viewer will call this '3'. And although the introduction is labelled '1', the viewer will refer to it as '7'.
To address this, we need to use a package designed for dealing with electronic versions of documents rather than merely printed ones. hyperref will address this problem and bookmark may optionally be loaded for enhanced, but more experimental, handling of bookmarks.
The following code produces the same visual output on the page but persuades the PDF viewer to label the pages correctly. This version also updates the deprecated commands identified by Harish Kumar in the comments.
\documentclass[a4paper,12pt,titlepage,oneside,final]{book}
\usepackage{hyperref}
%\usepackage{bookmark}% uncomment for enhanced, but experimental, bookmark handling
\usepackage{fancyhdr}
\fancyhf{}
\renewcommand{\headrulewidth}{0pt}
\fancyhf[cf]{\thepage}
\pagestyle{fancy}
\begin{document}
\frontmatter
\begin{titlepage}
{\bfseries Titlepage}\thispagestyle{empty}% note use of \bfseries replacing obsolete \bf command
\end{titlepage}
\pagenumbering{roman}
\stepcounter{page}% comment if the titlepage should not be counted
\clearpage% replaces deprecated \newpage
\thispagestyle{empty}
{\bfseries included pdf}
\clearpage
{\bfseries declaration}
\clearpage
{\bfseries Acknowledgement}
\clearpage
\thispagestyle{empty}
{\bfseries included pdf}
\tableofcontents
\mainmatter
\chapter*{introduction}
\pagenumbering{arabic}
\addcontentsline{toc}{chapter}{introduction}
\chapter{1st chapter}
\end{document}