Correct indentation in PDFWriter.

It had mixed tabs/spaces.
WL-2601 Don't write out null in text of PDF

When the department wasn't defined we wrote out null in the PDF. Now if it's null we omit it.
Tidy up the incorrect JavaDoc.
Merge pull request #103 from ox-it/WL-2601

WL-2601 Don't output null in PDF