I have some low quality scans of book pages, saved as a PDF, that I would like to enhance. Since they're text only, and the text is kind of faint, I think that using the erode filter on each page would probably work pretty well (it has in the past). The problem is, it would be nice to be able to use the erode filter on all the pages at once and not have to do each one individually.

When you open a single PDF page in GIMP, AFAICT, it imports it as an image file rather than a PDF, but I don't know what type of image. I installed BIMP to see if I could do a batch erode that way, but it wasn't able to do it. Is GIMP the way to go here, or would something like ImageMagick (which I know very little about) be better for this?