i dont know what this ddu is.is this is ur file name??ok watever.4 opening a .rar file u need to install winrar s/w and 4 .pdf file u need acrobat reader..both these s/w were easily found over internet 4 free downloading.
go 2 download.com and search 4 this under freeware section.
If you are using Windows OS means you can download the Acrobat reader and WinRar softwares, i had mentioned the source sites below source textarea.
If you are using someother OS means, please tell me, what is that OS