How to highlight lines on a document that is too long a scanned PDF to convert to OCR,

Using Acrobat CS6 suite - I have a large schematic that I wish to highlight various lines on it as a teaching aid for a seminar, but I can't use the Edit Text function as Acrobat complains the image is larger than the maximum 45 x 45 inches (it is longer).

I have tried to find  a way to highlight  individual circuits on the PDF using Illustrator or Photoshop or ? but I am too much of a neophyte to figure out that process so far. I assume I have to convert to .ai or something, and it would be nice if it could be in layers (but my eyes glaze over a bit when thinking about converting to layers) that could be turned on or off to highlight various sections. I will keep poking at the Adobe products in the hope of finding a workable solution in the meantime.

My goal is to have the same document with different highlighted parts depending on what exactly I am talking about to the audience - on screen and I can just click through each layer.

Is there a way to attach images to these Adobe forum questions to show what I am working with on a smaller scale?

I hope that explanation is clear enough! I have a couple of weeks to figure this out at least!

Thanks!