Certain pages in some PDFs, typically with images, don't show anything you draw. Sometimes it's only the text portion that can't be drawn on, other times the whole page. Annoying!
More detail: it's JPEG files that do this, AND you can draw over the jpg but not anyplace else on the page. Maybe a stacking issue? Or a bug in the pdf toolbox?
Certain pages in some PDFs, typically with images, don't show anything you draw. Sometimes it's only the text portion that can't be drawn on, other times the whole page. Annoying!