Hi IamAzhar,
The font file is not available in the hosting server.
So copy the ARIALUNI.TTF file and save in project folder. Then select the file from the project folder.
string fontPath = Server.MapPath("~/Fonts/");
BaseFont bf = BaseFont.CreateFont(fontPath + "ARIALUNI.ttf", BaseFont.IDENTITY_H, true);
For more details refer below link.
https://stackoverflow.com/questions/22728381/itextsharp-arialuni-ttf-copy-on-hosting-server