LuaLaTeX: How to reduce the file size of the generated PDF on the fly?

I’m using LaTeX to generate a PDF that will have around 1500 – 2000 pages. The PDF includes a lot of pictures. Approximately 5000 photographs (JPG) that are each 2MB and a couple of hundred smaller icons (JPG) that are around 500Kb.

Generating the first 400 pages results in a PDF with a size of 1.76GB. Generating more pages is not possible at the moment, since my laptop is running out of memory. What I want to achieve is to reduce the size of the generated PDF without touching the original images. Are there any options to set that I could use the reduce the size of the PDF?

I found a lot of similar questions, but all of them are taking about reducing the file size after the PDF has been generated. I need to do it on the fly.