Sending, copying or sharing a PDF, jpeg or any other file from windows to an ipad wirelessly and without using iTunes is quite simple.
We will use a program called HFS for this. It is only 600KB and does not need to be installed and the best of all it is free. Download here
double click hfs.exe and drag a PDF file from your file explorer to the HFS screen thats it. (note the ip address at the top of the HFS screen)
Now take your ipad and start the safari browser, type in the ip address in my case 192.168.1.8 click on the pdf and it will download on to your ipad it can be added to IBooks. (this approach will also work with other files)