Security handlers manage encryption and decription of PDF files. The
standard security handler uses RC4/MD5 to perform its crypto (AES as
well, but that is not yet implemented).
Add a unit test for each sample pdf file that currently exists in the
anon user's `~/Document/pdf` directory.
- linear.pdf
- non-linearized.pdf
- complex.pdf
Each test ensures that the pdf document is parsed and that the page
count is the expected one.
