If you e-filed your tax return, there is no written signature on the tax return. It was signed electronically. The electronic signature cannot be printed and does not appear in the PDF of the tax return. The people in the school's financial office should know this, but we often see that school financial office people are surprisingly ignorant of how tax returns are filed.
The easiest thing to do is to print the page that they want a signature on, sign it, and give them the signed copy. That should satisfy them.
