There is very good package available on Google code to create pdf files with plsql in Oracle, but some time people get confused because there are to too much links and example are there. That's why I am simply providing the code content to create pdf files with plsql.
Install this sql script to your schema and create the directory object that schema with the name MY_DIR, see the example below:
Create or Replace directory MY_DIR as 'D:AnyDirPath';
The below link I am providing for examples to how to use Pdf_Builder_Pkg for creating pdf files. The file contains plsql examples.