ASM programming

I'm relatively new to assembly programming and have a question regarding HC12 microprocessors. I understand the whole idea behind immediate addressing but say I want to...
PRINTF EQU $EE88

LDD #STRING
LDX PRINTF
JSR $0,X
...
STRING FCC 'blahblahblah'

Why when I'm trying to use the variable string do I have to use imm add to to put the address in D whereas when putting the address of PRINTF into X I do not have to use imm add?

Does that snippet work as you expect it to? The LDX instruction would load the value stored at $EE88, not load the value $EE88 into IX.