How to highlight / draw onto a pdf document that is a scanned image, then save the added elements

Hello

I'd like to add markings / little annotations or highlight as if with a color marker various sections of a scanned image that has been sent to me in pdf format, which I visualize with Adobe Reader 9 on my PC (Windows). I need to save the changes and then send it back by e-mail to the original sender.

So far I've been awkwardlky making copies of my screen (PrintScreen function) of each individual page of the pdf document, then pasting them into PowerPoint slides, then using various PPT drawing and textbox functions to add my stuff to the, now, PPT file, which then I sent back as such. This is very time-consuming and ridiculous and there's got to be another way of adding these changes within Adobe Reader or another similar software, doesn't it?

Again, the pdf docs that I need to work on are scanned images (medical charts), not actual copiable text (pardon my ignorance of the correct terminology to explain this).

Thank you for your help,

Falingo