PDFCreator is a free tool to create PDF files from nearly any Windows application.

Features:

Create PDFs from any program that is able to print
Security: Encrypt PDFs and protect them from being opened, printed etc
Digitally sign your PDFs to ensure that you are the author and the file has not been modified
Create PDF/A files for long term archives
Send generated files via eMail
Create more than just PDFs: PNG, JPG, TIFF, BMP, PCX, PS, EPS
AutoSave files to folders and filenames based on Tags like Username, Computername, Date, Time etc.
Merge multiple files into one PDF
Easy Install: Just say what you want and everything is installed
Terminal Server: PDFCreator also runs on Terminal Servers without problems
PDFCreator is free, even for commercial use! It is Open Source and released under the Terms of the GNU General Public License.
Supports Windows Vista and Windows 7