To convert doc to pdf in Mac OS X follow the steps below:-

• Open your doc file with your Text Editor (ex: Ms Word, TextEdit, Writer, Excel, Open Office etc)
• Click on File -> Print or Press Command + P
  
• Print Window will pop up, click on “PDF” button at the bottom left and select “Save as PDF …”
  
• Choose the location you wan to save the pdf file and click “Save”
  
• Done, you just convert your doc to PDF file

** If you find the pdf file size big, then you might want to read my post about how to reduce pdf file size in mac os x

** This method is not only limited to convert doc to pdf, but also allow you to convert almost any file to PDF. **