Yeah sure. There's lots of ways to do that. Depending on your NAS, you may be able to do that directly from the web browser. Put the IP of you NAS in the web browser.
A better solution, that would offer ease of transferring files to and from, would be an app like
Filebrowser. That will let you save to and from the iPad easily. I use this app on occasion, and it's pretty handy. It has templates for connecting to different devices like WinPC, OSX, Linux, NAS, etc.
It also lets you attach any file and send it as an attachment from the iPad. Which is a really handy feature since you can't do that natively. Select any file from the iPad's Home folder, or from your NAS once that's connected, click on the file where it has a little (>) arrow, and a dropdown appears where you can attach that file in an e-mail.
You can even forward a port through your router, and have that available away from home. So you could access your home NAS from work and such.