Slowly displaying PDFs on remote desktops is a very common issue when using RDP. I recommend you look at Ericom Blaze, a software product that accelerates and compresses standard Microsoft RDP. Blaze accelerates RDP performance by as much as 10-25 times, and helps deliver higher frame rates and reduce screen freezes and choppiness.
You can read more about Blaze at:
Or view a video demo at:
Hope this helps.