How to launch pdf viewer from the terminal I'm working using LaTeX, since I compile the document in the terminal, it would be much easier for me to open it in pdf viewer directly from the terminal.

I'm using OS X 10.8.2 in Polish, so I'm not sure of the English name of the viewer I'm using, but it's the default one, I guess it's Preview in English. But the command preview &lt;filename.pdf&gt; results in -bash: preview: command not found.
You can just use open &lt;filename.pdf&gt; and your OS will use the default program to view PDFs. With open -a Preview.app &lt;filename.pdf&gt; your PDF is opened using Preview, even if your default PDF reader is something different.