How do I upload photos from my iPad to my desktop?

There are a number of ways including:

via USB cable: Import photos and videos from your iPhone, iPad, or iPod touch to your Mac or Windows PC - Apple Support

via 3rd party apps such as http://www.photosync-app.com

via Photo Stream (for new photos taken after you turn on Photo Stream): My Photo Stream FAQ - Apple Support

& iCloud Photo Library beta FAQ - Apple Support

Do you want to transfer the photos as they have been taken with the iPad's camera, or do you want to transfer edited photos with effects applied?

if you want to transfer edited photos to a Mac, share them using Mail, see this link:

iPhoto and Aperture don't have edits to photos you import from iOS 8 devices

Transferring via Photo Stream or USB cable will transfer the unedited original photos.