This is have been truly cumbersome, and i've done a lot for research about it but ended up failing to solve it.
as you can see in the print-screen, this path entered in the Header Path Search and it contains all the .h files have been installed with PoDoFo including podofo-base.h as well as PdfVersion.h
However, I don't know why i'm getting this?
i read A LOT of solution with EL Captain but non of them worked with me as i have Sierra. also those solutions were for xCode 7 and earlier versions.
Please help!