After having uploaded a pdf-document in the internet small boxes appear in the text

After having uploaded a pdf-document in the internet small boxes appear in the text! What is the fault and how to solve the problem?

I have got a pdf-document from a publisher and forwarded it to METIS (University of Amsterdam) so that it has been uploaded there compare http://dare.uva.nl/document/505726

But now those small boxes appear f.i. on page 70, 74, on the last page etc.

The problem does not appear if somebody opens the download at https://www.academia.edu/3754512/Eine_queere_Lekture_von_Josef_Judisch e_Interpretationen_des_schonen_jungen_Manns_aus_der_Hebraischen_Bibel !