I highly recommend ScanTailor. The software hasn’t been updated since 2013, but it’s free, open source, 64 bit, and does exactly what you’re looking for and way more. (I used it to split and clean up photocopies or scans of books.) When it eventually stops working, I will be incredibly sad, because nothing matches the power of this tool.
Thank you for this. I had used a Alfred workflow that ran some dark-magic scripts through the free PDF app “Skim”, several years ago, that did something similar. Doubt the workflow still exists.
Just downloaded and tried PDFCutter, and works a charm.
I still have plenty of PDFs inside DT3, digitised from old photocopies of various book chapters/articles collected over the years, that this will prove very useful for.