OpenOffice has the functionality to use extensions: snippets of code that add extra features to the program. One useful extension is the Oracle PDF Import Extension. This lets you open a PDF like any other document in Draw and make changes to it. You can then save in the range of standard formats, including PDF.
The second extension is Writer's Tools:http://code.google.com/p/writertools/downloads/list. Writer's Tools gives you a new menu in OpenOffice that let you do a range of things, like backup or translate.
Writer's Tools is a very useful addition to OpenOffice
The backup supports FTP, email and Amazon, you can bookmark documents and lookup words. Beware that this extension needs some setting up however, though it is easy to follow the instructions.
Please comment if you know about any other good extensions as I haven't written much here.