I have a PDF that needs a very small tweak: four headings must receive a clean underline that sits exactly at the same hierarchy level as the text itself. I already have the original source file, so you can work from whichever format is quickest for you, then export the result back to PDF. Please keep the final PDF locked down—non-editable text is what I need—while preserving every other layout element untouched. Send back the updated PDF plus the adjusted source file once you’re done. This is a quick, low-complexity task, but doing it smoothly could lead to more layout work together. Thank you.