Make sure your Excel graph is on one individual sheet, not within a spreadsheet. Then choose File → Save as Adobe PDF.
When combining multiple graphs you need to select the cells around the graph and then use File → Export → Create Adobe PDF. There you choose “Selection” and “Fit to paper width”.
Please ensure you send us only EPS, PS, or PDF files. The easiest way (if the above doesn’t work) is to print the file to the Adobe PDF printer or distiller with fonts embedded. DO NOT USE THE PDF-writer. Do not simply convert Excel files into TIFF-files; that just makes them worse!
