Visually Comparing Two PDFs Quickly

While I was preparing to submit my most recent manuscript, I had to quickly add line numbers. It just took a couple of lines in the LaTeX source file, but I was worried that doing so would subtley mess up the document in some way that I&rsquo;d only realize after it was too late. To ensure that the two documents were identical but for the line numbers, I just overlayed them using pdftk and the…