Another way to convert Windows Metafile to PDF is using PDFDCEX. This approach has a few advantages (like better conversion etc) over PDFDC/FromEMF():
PDFNet.Initialize();
using (PDFDCEX pdfdcex = new PDFDCEX())
using (PDFDoc pdfdoc = new PDFDoc()) {
string emf_file_path = input_path + "simple-emf.emf";
pdfdcex.Begin(pdfdoc);
using(Graphics gr = pdfdcex.StartPage()) {
using(Metafile img = new Metafile(emf_file_path)) {
gr.DrawImage(img, 0, 0);
}
pdfdcex.EndPage();
}
pdfdcex.End();
pdfdoc.Save(output_path + "mem_test.pdf", SDFDoc.SaveOptions.e_linearized);