The easiest way is to use some web storage like box.net, dropbox, 4shared, etc - upload the pdfs to your storage space with whichever free service you pick, then download them to whichever app your plan to read/edit the pdfs with on your iPad.
Note that there is no general shared file space on the iPad, so you will need to load them directly into the app you use with those files (Adobe reader, GoodReader, GoodNotes or whichever app you use for your pdf files).
If you sync with iTunes on your computer, many of those apps will also allow you to simply drag and drop the files into them when your iPad is connected to iTunes, then click on sync, and they will be transferred over.