You can do it in iTunes. In the left panel, click on your iPad's name (should be something like Joe's iPad or whatever). In the main panel on the right, you'll see "Apps". Click on it and scroll to the bottom. You'll see a list of a few apps depending on what you have installed. Choose the one you'd like to be able to open it in and add the file.
Definitely one of my least favorite things to do.
Can you move files (ppt, word, excel epub) from your pc to the ipad 2?
If so, how?
iBooks reads epub. I think you add them into your library normally once you've installed it (File > Add files to library, something like that).
GoodReaders reads a lot of files, including .doc, .ppt, etc. I think it even reads zip files. You just can't edit them. Pages is my preferred word processor, but it's also the only one I've tried. I don't think it reads the new Office extensions though (.docx, .pptx, etc). I could be wrong.
Can you move files (ppt, word, excel epub) from your pc to the ipad 2?
If so, how?