Different apps will have different ways of copying their content to/from a computer, so it will depend upon what the apps that you want to transfer the files to supports e.g. via the file sharing section at the bottom of the device's apps tab when connected to iTunes, via your wifi network, email, dropbox etc.
Syncing music : http://support.apple.com/kb/HT1351
Syncing apps : http://support.apple.com/kb/HT1977
Syncing photos : http://support.apple.com/kb/HT4236
Copying photos from the iPad to your computer : http://support.apple.com/kb/HT4083
You will first need an app on your iPad that supports text files - unlike a 'normal' computer the iPad doesn't have a file system, and everything on it has to be associated with an app. How you then get the file to that app will depend upon what transfer method(s) that the app supports (file sharing, wifi network etc)
You can do that with Apps
1. Goto Share and Print
2. Send to iTunes
3. Choose what kind of format you want to export
4. Plug it into your Mac and goto App, then you will see your exported files under Pages
What's more, you can refer to below page of transfer files from macbook to iPad, which includes transfer music, pohtos, contacts, and videos and more.