Thank You, this is it :)
WIth an External Process using Python, something like:
import shutil
import sys
name = sys.argv[3]
newname = name.replace(' ','_')
shutil.copy(sys.argv[1],'C:/Temp/' + newname + '.pdf')
where sys.argv[1]=$FFin$ and sys.argv[3]="$FFwfJob.jobName$"
There is no known character number it is variable
If one knows what character number the space is located at, substringing could be used for the Save node's filename. For example:
$FFwfJob.jobName.substring(0,4)$_$FFwfJob.jobName.substring(-3,3)$