If one knows what character number the space is located at, substringing could be used for the Save node's filename. For example:
$FFwfJob.jobName.substring(0,4)$_$FFwfJob.jobName.substring(-3,3)$
There is no known character number it is variable
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]="$FFwfJob.jobName$"
Thank You, this is it :)