Printing is black magic. One common issue is that you don't have all fonts embedded in the PDF file. There may not be anything wrong on screen, as the PDF read

Printing is black magic. One common issue is that you don't have all fonts embedded in the PDF file. There may not be anything wrong on screen, as the PDF reader can probably find the font if you have it installed. But the software you use for printing may not know enough about the capabilities of your printer, and it may choose to hope for the best. If your printer does not have the font and the printing software didn't bother sending it with the document, the printer will use another font as a substitute.