Clean scanning is hard but for something that simple... As an invite to post-processing (i.e. ScanTailor on GNU/Linux|FLOSS) https://jmp.sh/s/kaK1yCvKuuJa9sRGCSFg
If you didn't now it, give ocrmypdf (python/tesseract wrapper) a try, all you need is `ocrmypdf in.pdf out.pdf`. It's not super-perfect but works well enough in 99% of common cases.
Thanks for that, original pdf was so saturated I had to close after reading 2 pages.