As I assumed: when I reselect the appropriate weightnaming in the stylesheets, the problem is solved. I had to check in the Xpress doc what the used weights were.
The font's weightnaming comes up different in Xpress than it is in ID2 (fi: 'KinesMM_380 RG' in Xpress is 'Kinesis MM Roman', weightnaming 'regular' in ID2).
So somewhere along the line of conversion, ID2 decides to set that naming to *[0]*, and when PDF-ing, as a result ID2 can't embed the font.
OT are you still using Delta?
You mean Delta from Heidelberg? No actually not. I switched from job. The last system I was using was Agfa's ApogeeX 3.5. Do you have a particular question regarding Delta?