How to effectively compress an image (scan, pdf)?

Question

Scanning

The office has 2 MFPs - Kyocera FS-1028MFP KX and Xerox WorkCentre 7525. Both are with network scanners. The first is configured and scans at 200 dpi, the second at 300 dpi. But with approximately the same image quality, the scan size differs by about 6 times. Here are the samples.
From time to time there is a need to compress scans made on Kyocera, or scans received from contractors, with a minimum loss of quality. It is most often impossible to rescan on Xerox - the originals are either no longer there, or they are filed and scanning a 30-page contract becomes very laborious.
Actually, the question is: how (what program) can compress an image as efficiently as Xerox does?
Online services are not interested - the documents are confidential.

Answer 1

There is a good article about how to use the PDF optimizer here: blogs.adobe.com/acrolaw/2009/08/reducing-the-file-...
Unfortunately, I have no way to install it now and check its effectiveness.
From my own experience, if the file is scanned "incorrectly", optimizers will not reduce it without significant loss of quality.

Answer 2

Click to djvu. Read man c44, man djpeg, etc.

Answer 3

The best format for scanned texts is djvu .

Answer 4

"save for web" in photoshop