How to customize a content type css? I have a pdf sharing site with a content type which called PDF. This content type has many fileds (such as author, description, rating, etc). These fields display in simple rows but I want to change either their form and css. for example I want to show Rating number much bigger (and in other color) on the top of each post. what can I do?
Am I able to define new css classes for these fields?
create a new template file and add any classes you want. Here's a good introduction to D7 templates.

your template should be named like this: node--node_type.tpl.php. In your case, I think it should be node--pdf.tpl.php. You can use node.tpl.php as a starting point