What is the crowd's opinion of PDFpen?

From 3.5 billion comments

Yes, PDF Expert decided to become ransomware some time back, and that also made me drop it and look for alternatives.

I’d suggest taking a look at LiquidText for annotation and notes on papers, etc.

And for a general PDF editor (fill out forms, …) I use PDFpen

Both LiquidText and PDFpen support iPad/iPhone and MacOS

I used PDFpenPro ( https://pdfpen.com/pdfpenpro/ ). I was fortunate that the scans I had of the original parts were all pretty straight, and all at about the same scale, so I was able to just select measures from one PDF and drop it into the other PDF, and it usually just worked.