The Generate PDF service cannot change one font face to another, but the Output and Forms services can. If your LiveCycle installation includes one of these services, you can add <equate> elements to the default XCI document that they consume. For example:
<equate from="Helvetica Black_*_*" to="Arial Black_*_*" force="0"/>
<equate from="HelveticaBlack_*_*" to="Arial Black_*_*" force="0"/>
<equate from="Helvetica-Black_*_*" to="Arial Black_*_*" force="0"/>
<equate from="Helvetica_*_*" to="Arial_*_*" force="0"/>
<equate from="Helv_*_*" to="Arial_*_*" force="0"/>
I have to admit this solution is along the lines of using a cannon to kill a mosquito or cutting the butter with a chainsaw. I picked up these terms from other LiveCycle forums. It's amazing what you learn from these forums.
For more information, see Designing Forms for Output ES.