How to create PDF file with all your bookmarks displayed?

According to the documentation of bookmark you can use the open option; if you want to set the level, you can say openlevel=<level>; so

\usepackage[open,openlevel=1]{bookmark}

will show something like

whereas the simple open option will show

Tested with Skim and Adobe Reader on Mac OS X.

Simply add bookmarksopen=true for the default bookmarks-open to also expand them. I will refrain from posting a screenshot as my viewer ignores all these options anyway and acroread simply takes forever to even consider possibly thinking about sometime in the distant future opening a file. (But the OP confirmed that it works in Adobe's viewer.)

\documentclass[12pt]{book}

\usepackage[colorlinks=true,linkcolor=blue,urlcolor=black,bookmarksopen=true]{hyperref}

\usepackage{bookmark}

\begin{document}

\chapter{Chapter [One}
\section{Section two}
\subsection{Section one}
\subsection{Section two}
\section{Section three}
\subsection{Section one}
\subsection{Section two}
\section{Section four}
\subsection{Section one}
\subsection{Section two}
\subsection{Section three}

\end{document}