Can't copy text displayed by component

I have a pdf file in version 1.4 that cannot copy the content (text) of the file when it is opened by the component. 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).
This pdf is generated by pdf sharp core ( https://github.com/ststeiger/PdfSharpCore ) v1.3.32.