The PDF format is diverse enough for such a new project to still have plenty of incompatibilities. If you wanted to find many of them quickly, you might want to

The PDF format is diverse enough for such a new project to still have plenty of incompatibilities. If you wanted to find many of them quickly, you might want to have a look at the documents used as test cases in other projects, such as pdf.js: https://github.com/mozilla/pdf.js/tree/master/test/pdfs https://github.com/mozilla/pdf.js/tree/master/test/pdfs