Simplest way to transfer photos from PC to iPad (not sync-all)? I'd like to transfer selected photos from my PC to an iPad Air 2 running iOS 9.2. This thread shows how to transfer from iPad to PC (Use Windows Explorer and treat iPad as a camera), and this thread suggests using Dropbox.

Can I use Windows Explorer and have the photos show up in the camera roll on my iPad? If not, what's the easiest way of doing so without syncing?

Note: I can see and copy JPGs from the iPad to my PC with Windows Explorer. I am not able to copy from my PC to the iPad.
The easiest way to get photos from a PC to an iOS device would be backing up certain photos to a cloud service like Google Photos or Dropbox. There is no way to get photos from PC into the iOS Camera Roll that I am aware of. Check out Google Photos. It would be the most seamless solution.