When I email pdf invoices to people with Apple computers they often complain some of the important text (e.g. banking details) are missing. 

The standardized aspects of PDF are fairly universal however, there are some non-standard advancements that have been added to the format, both by Apple, Adobe, and others. If someone forgets to check the setting for embedding a specific font, then that font may not show up on a system that does not have it.

To fix this problem:

• Click on  Debtors  >  Invoices  menu option
• Double click on the invoice to open
• Click on the  Print  button
• Click on the PDF icon

• In the  Export to PDF  window, make sure the  Embedded fonts  check box is ticked
• Click on the   OK  button
  

• Save invoice to the appropriate file location
• You can now attach the saved pdf file to an email