Sometimes you simple need all your drives on your desktop, but the ones like ‘TimeMachine’ or ‘Lion Installer’ can also simple disappear. Use this script to hide them at every reboot, without having to unmount them. Adjust your volume name to reflect yours.

sudo echo "echo \"UUID=$(diskutil info /Volumes/Lion\ Installer/ | grep UUID | awk '{print $3}') none hfs rw,noauto\" >> /etc/fstab" | sudo bash

To see if it has worked:
sudo cat /etc/fstab

Results in:
UUID=F4F6562F-1C4D-361D-BBD4-91C12ED96B44 none hfs rw,noauto

If your /etc/fstab doesn’t show the UUIC, then you need to check the volume name and/or delimit spaces with an \.

The newer versions of Preview (at least OS X 10.5, and maybe earlier) respect the “do not print without a password” setting in PDF files. However, it is possible to create a completely unprotected version of any PDF file using ghostscript. A command like this should work:

gs -sOutputFile=MyNewFile.pdf -sDEVICE=pdfwrite -dNOPAUSE -dbatch -q MyProtectedFile.pdf

You may need to type “quit” at the command prompt after gs finishes processing the file. Then open the newly created PDF file and voilà, printable!