The answer to “can I change … in PrintDraft?” is basically always “yes”. The real question is whether it’s worth it for a draft since these sorts of things can rarely be tweaked from within Paratext itself.
This particular question is strange since the default on that gap should be much smaller. It would seem like you’ve already tweaked it somehow.
What you need to do is go to your “Paratext Projects/XXX/PrintDraft” folder (where XXX is your project code) and find the PrintDraft-mods.tex file and open it in a text editor. Find the line that has "%\def\TopMarginFactor{##} in it.
If that line does not have a % at the beginning, add it and save the file (make sure you’re saving as a plain text document in Unicode format). Then try re-running PrintDraft and seeing if that fixed it.
If it does have a %, try deleting it and changing the ## inside the { } marks to “1.0”. Save. Run PrintDraft. It that works you may need to experiment with the exact value that will look best. It will probably be between 1.0 and 1.5.
