Add a reduced test case for PR 5286

When submitting PR #5286, I didn't include a test case. The reason was that I wanted to avoid adding a linked test, since most of the issues referred to files at various hosting services (hence with uncertain future availability). Manually creating a test case seemed "hard" so I just skipped it, which is obviously bad since it greatly increases the risk of future regressions.

However I recently noticed that for one of the PDF files it was possible to easily, using only a text editor and PDFtk, remove any potentially sensitive content and still have a meaningful test case, hence this patch.