You should buy Acrobat DC
https://helpx.adobe.com/acrobat/using/compare-documents.html
A few months ago my collegue who is in charge of business addministration (non programmer) asked me for PDF comparison solution. He wanted a view where the differences in 2 PDF documents are visually highlighted and easily seen. I looked at several commercial products and a few open source projects for PDF comparison solution. I found Acrobat DC provides intuitive view of hilighted differences. I thought Adobe DC is the best for him (non-programmers). I know Adobe DC charges a small amount of money but, I think, it is worth paying if PDF comparison is a serious problem for business.
However Adobe DC might not be fitting If you are interested in PDF comparison integrated in automated UI tests driven by Katalon Studio.