Generating PDF File

I am a newbie to Java and looking for an easy way to generate a PDF file.

I need to populate the PDF with multiple tables having columns and rows.

Also be able to render text headers outside the tables.

Is there any open source library i can use for above purpose?

I did some research online and found some libraries. But the problem is that, am not able to find much documents on how to use those lib's.

The main purpose is to add tables in PDF and this lib should have proper documentation on how to do that!