You can always just email to yourself as an attachment and open the email and attachment on your pad email in whatever app you want to read it with on your iPad. I believe iBooks will read PDF, the Kindle App, GoodReader, maybe Pages. Some are free, some come on the pad, and others you pay for, ie GoodReader.
Some you can transfer by attaching your pad to the computer with iTunes, but instead of syncing, click the Apps tab and scroll down to the bottom and find the app, say GoodReader, and click it. Click to add files and locate the file you want on the computer and add it to your GoodReader. You can add files to the computer from GoodReader this way, too, if you downloaded a file from the internet to your pad and don't want to just email it to yourself. Done the same,,except select to,transfer the files from the pad to the computer. Much like copying files from one folder to another with a file directory.