Free PDF markup tool
I had to markup a file I had in PDF-only format, and a quick search turned up an incredibly powerful and FREE (even for commercial use) tool called PDF-XChange Viewer. In addition to being a lightweight (4MB) and fast PDF viewer (with a portable version and with IE and FF plugins), it also provides markup tools like highlighting, text boxes, comments, and drawing.
For Windows, of course.
Just loving it! Thanks for the tip, uninstalling the big and slow Adobe software..