What should I do when one of my PDFs is crashing PDFpenPro?
The original document may be off-spec, or you may have uncovered a bug. Please try opening the original in PDFpenPro then do File->Print->PDF->Save as PDF… Open the newly-saved document and perform your edits. If that works, please consider sending us the original document so that we can analyze why and hopefully make PDFpenPro handle that more gracefully in a future release.