I've just had to draw two crosses on my PC screen so I could line up the page numbers I was adding to a 36 page PDF document (and then rub crosses out again, of course). The application I was using didn't seem to have a way of repeatably getting things in the same place on a series of pages. This made me think, why doesn't someone produce a little application which allows one to put on the screen horizontal and vertical guides (or lines, or boxes, or other alignment marks) similar to the ones you get in Adobe Illustrator or CorelDraw, but in a transparent window so whatever's displayed by the underlying application shows through (and of course the mouse ought to control the underlying application)?
Does anything like this exist?
It sounds like a useful add-on to one of those screen rule/protractor applications.