You can get files onto your iPad in various ways:
1. Use a cloud based service like iCloud, Dropbox, Google Drive, etc.
2. Transfer the files directly thorugh iTunes. Keep in mind with this method not all file types are supported. iTunes is only used to transfer media like music, videos, ebooks, ringtones, etc.
3. There are 3rd party apps out there that you put on your computer that will enable you to tranfer or remove files from your iOS device. I've mainly only used these types of program for iPods and iPhones, but I assume they will work with an iPad the same way.
4. You can transfer files with a portable drive that has built in wireless/streaming connectivity. Companies like Kingston and Seagate make these drives. Some are basic hard drives while others are media drives that take portable flash media.
In your case, it sounds like you are simply wanting to transfer the files onto the iPad and not actually store them permanently on external media, like a USB drive. Since the files you are wanting to transfer are native mac application files, Numbers & Pages, then the easist solution is through iCloud or Dropbox. Of course, to work on these files on your iPad you will have to install the Numbers and Pages iOS apps on your iPad as well.
I hope this info helps. Let us know how things work out for you.