You can use the makecab command in Windows to compress files. Enter the name of the file you want to compress, followed by the name of the new compressed file. See this example:
makecab B_Obama_2013.pdf B_Obama_2013.zipp /v
As you can see a new, smaller file is created. This can be opened in a file compression program like WinZip.
The /v option simply controls how much information is shown about what Windows is doing.