I have a large black and white pdf scan of a book. The book is 1700 pages, and is about 300MB. That is about 150-175kb per page. This strikes me as rather large. Two arbitrarily selected pages are attached to illustrate; they are each about 330kb. Running them through ImageMagick's compressor gives pages which are about 240kb, which I think is still too high. The best I've been able to get is about 33% smaller. Very good but still very bad in absolute terms.
I believe the book is simply a bunch of .png's stitched together with no more information than that. I have tried converting to a lower dpi, but it really decreases readability beyond 300. I am confident there is to be a way to convert these files to some kind of document (either .pdf or .djvu), but I don't know how to do this. I tried converting to .tif and that was very useful.
I have done some research and it seems that it might be helpful to run these images through some kind of OCR text recognition software, or otherwise construct "vectorized" text. Can anyone help me with a recommendation of an open source tool for this and some instructions on how to get started?