Can't copy text displayed by pdf embed

[Kallyl5E13]

I have a pdf file in version 1.4 that cannot copy the content (text) of the file when it is opened by the pdf embed. I have already opened the file locally (Adobe Reader DC) and there it is possible to copy the content (text), I also opened the file in the browser (Chrome) and also allows copying the content of the file (text).

[Kallyl5E13]

This pdf is generated by pdf sharp core (https://github.com/ststeiger/PdfSharpCore) v1.3.32.