I don't know whether you still have this problem but I generally get this error when I have set up a template with fonts that are either faulty or non existent at the time I create/send the report (invoice, etc).

The way to fix this for me is to carefully go through all the fields (text and variables) in the report(s) and check that all fonts used are actually installed and active on the system.

I have the same issue, but the invoice will print just fine and I can even use the mail PDF function in the Print window. It is just the email invoice function that has the error. 

Just spent four hours carefully customising and styling the invoice to be the serious document that it needs to be consistent with the new corporate look. Constant checking through the design stage and now that it has been approved its destroys its design as soon as you try to send it to the client. AARRRRRGGGGGHHHH!!!!!!

The fonts ARE on the computer that has the template and that I am sending them from and done all the customisation on. The fonts are not on the server client of studiometry. Installing them there now but I somehow doubt that is the issue. 

Using the print option: its fine. Saving a PDF when using the print option: fine. Mail pdf from print dialogue: fine. 

Use the "Email" option (which is the most preferred option) it loses its fonts, sizes and leading information. 

Export: It loses its fonts, sizes and leading information. Not Pretty. Tired and underwhelmed. 

I had the same problem. When exporting an invoice as a pdf, Studiometry does´t find many of my installed fonts.

They only work, when I manually copy the font files to:

/system/library/fonts