Touch up scan and cleanup Architecture blueprint plans

I have old architecture plans that have been scanned. They are somewhat faded and have some handwriting. I want to clean them up in Photoshop so they can be printed like artwork. Attached image is a low-res version of the scan of the original plan.

I AM NOT looking for re-creating the drawing, vector line art, or any new drawing. I want to preserve the original hand-drawn lines but make it more presentable to be printed for wall art.