I have pages of handwritten notes that I decided to scan to a PDF. Somehow, 153 pages of notes turned into a 156.4 MB PDF file.
The notes are scanned in color because I used four different colors: black, red, blue, green. In fact, the only colors I really need for the document are those four (plus white). Is there a way to reduce the number of colors in the PDF file? (e.g. via a Unix command?)