The look
A signal, not an obstacle
A heavy mark makes the document unreadable; a very light one passes without anyone noticing.
Size
One word across a third of the page is enough. A mark that fills the page forces the reader to guess between the letters.
Angle
A diagonal separates the mark from the text visually, so the eye reads both without them interfering.
Opacity
Something in the middle: visible at a glance, not annoying in continuous reading. Black-and-white printing loses part of the gradient, so try a printed copy if the document will be printed.
What usually goes with the mark
- Page numbers so people can refer to pages during the review
- Merging the document with a covering letter before sending
- Extracting the pages that need review on their own