How to find and replace text in a pdf file?

Question

PDF

There is a pdf document in which it is tedious to find text and replace it. I tried javascript and java examples, as well as pdftk + sed utilities. Nothing helps, the text does not change. Because of what this could be. What libraries for js and java and / or utilities for linux do you recommend? Already tried hummus (js), pdfbox (java) and itext (java), as well as the utilities mentioned above. Nothing helped. The Pdf document on which I am testing contains the desired text and is located by a simple search in Adobe Reader.