Hi Argento, if you get email on your iPad, just email it to yourself and then you should be able to simply open it in iBooks on the iPad. Another way would be to get yourself a Dropbox account ( it's free) and transfer it that way. I'm on a Mac not PC so I was able to simply open the downloaded PDF in iBooks on the Mac and then it was picked up by the iPad when I synced.
Hope this helps