How to update the program "preview"? Im Using Mac OS X 10.6.8 and I do regular updates via "apple-symbol / Software Update ...".

For Viewing an printing PDFs, I use a program called preview. The version installed on my computer is "5.0.3 (504.1)". On Wikipedia I found, that the current version is 7.0. How can I Update to this version?
The version is linked to your OS level, you are using an older version of Preview because you are using an older OS.  The latest version is available as part of the latest OS.  Luckily, this update is now free, so long as your machine is compatible - looks for OS X Mavericks in the App Store