I kind of found a roundabout way to take a PDF and turn it into a schematic, or at the very least, an image that can be superimposed onto a schematic. As a test, I took a PDF of a schematic, and I converted to a bitmap. I then used KiCAD's worksheet editor, loaded the bitmap into a template, saved the template, and used the schematic page settings to load the template. You can see the results below in my ZIP file. It took a lot of steps, and it was a bit roundabout, but that's one way to take a PDF of sorts and convert it into a schematic (if not an actual schematic, at least a guideline for a schematic).
This method seems handy, especially for taking really old schematics and trying to rebuild them. Rather than redraw them by hand, this gives a guide to make things easier. I was wondering if anyone had some tips to make this process smoother or more accurate? Or maybe there's a more direct way to convert a PDF to a KiCAD schematic? I thought this was kind of cool, so I thought to share it.