does ipad mini have a usb port? if not then how can i share my documents with devices other than apple?

Install Dropbox on all devices and share your photos, videos and documents.

No USB Port on the iPad. You can email documents to other non iOS users. Apps like DropBox will work as well.

I also use a wireless flash drive to share files with all my devices.

http://www.sandisk.com/products/wireless/flash-drive/

Wireless Flash Drive (tap to enlarge image)