Word to pdf conversion: problem with Gill Sans MT

I had a 10 year old macbook which i have just upgraded to a new macbook air. Converting from word to pdf has never been a problem. Today, I did the same and in my header: RAB (in Gill Sans MT) the A and B come out all right in the pdf but the R is a square box. Can anyone help? The A and te B are also in Gill Sans MT. As its our company header, it stops me sending any documents out in PDF which is a real problem. 

I'm running Sonoma 14.0 btw.

Would be really grateful for resolution.

TIA