Can I pair an iPad Pro version 4 with a first generation pencil?

The 4th generation iPad Pro only works the the Apple Pencil 2nd generation.

Apple Pencil compatibility - Apple Support

Apple Pencil (2nd generation)

You can use Apple Pencil (2nd generation) with these iPad models: 

• iPad Air (4th generation)
• iPad Pro 12.9-inch (3rd generation) and later
• iPad Pro 11-inch (1st generation) and later

No that generation of iPad Pro can only use the first generation pencil.

~Lyssa