I have many old scanned PDFs which take up too much space on disk.
I have tried many PDF compressors available on the web. All of them ask me what compression to use for color images, and what to use for monochromatic images; but I could not find anything to convert EVERYTHING to a binary image.
By binary, I mean that each pixel can only have one of 2 color values: full black or full white. I know that all my PDFs have black/white text (not even grayscale). Can some tool (windows or linux or android) use this knowledge to achieve better compression?
I'm not sure, but "Optimize PDF" tool in Adobe Acrobat Pro may do what I want. However, even if it does, I would prefer to know about a less expensive and a more compact application.