@Xarathustra You can kind of but best to have a good reason behind it. This was just a Text-less one that I never got done with that someone can maybe use. Now I don't understand the "proper leveling" thing I just use GIMP as for making them into PNG format that's No problem just this was done in JPEG format long ago and I did not think about changing it.
Do not touch leveling, let the editors and typesetters that know what they are doing touch it (what's supposed to be the scanner job), you already do the heavy lifting as a cleaner, keep the good work