So I created some folders on my homescreens, that have pdf's in them I was wondering is there a way to plug the phone in to the computer and drag all 20 pdf's to that folder instead of having to move them one by one
If you mean you added a "Folder" from the Personalize menu, then that's different than a real folder on the SD card. I don't think there's any way for you to do what you want with such a folder.
However, with Astro File Manager (a free app), you can add a shortcut to a real folder on the SD card. When you click on the shortcut on the home screen, it will open the folder in Astro File Manager and you will be able to see all the files. You should be able to click on a PDF file had have it launch the viewer.
To create an Astro File Manager shortcut to a folder, you either have to long press on the folder in the list it shows you, or you have to short press on the folder and then quickly press the "OK" button that pops up for a second or two when it navigates to the folder before the buttons disappear again.
After doing this, you should be able to use your PC to copy files into that folder and then access them from the shortcut on your home screen.