This article shows how to use OpenMem method to open pdf with data (note: the pdf will be readonly).

            //Open PDF from Mem demo
            const char *path1 = [pdfFullPath UTF8String];

            FILE *file1 = fopen(path1, "rb");
            fseek(file1, 0, SEEK_END);

            long filesize1 = ftell(file1);
            fseek(file1, 0, SEEK_SET);

            buffer = malloc((filesize1)*sizeof(char));
            fread(buffer, filesize1, 1, file1);

            fclose(file1);

            int result = [m_pdf PDFopenMem: buffer :(int)filesize1 :nil];