ZTPad 285 C94


Hi guys. I have a ZTPad 285 C94, cortex A9 Quad core. Android 4.0 mobile Operating System. I have a problem. I am inside of a circle. I explain you: when I download any file from my mails (pdf, word, excel,....) I can not read it. When I try to instal any soft for read or open that file (example Documents to Go) I can download, but I can not open it because it is compressed (.rar or .zip) and my tablet does not come with winzip or winrar. The tablet has microSD port, usb port. What can I do to start to enjoy my tablet? usb way, microsd way? Download pc via, decompress on microSD, insert microSD to may tablet?
Thanks in advance
Virgilio Gonzalez