Thanks for checking it out. I was beginning to feel like Chicken Little. I too saw the .ttc designation in checking the File > Properties panel of the Acrobat Reader PDF-x-1a export. I thought that the .ttc extension was something that Adobe had assigned to designate "Custom" when instead it had substituted Arial.ttf. This further deepened my conspiracy theory about Adobe until I was told that Adobe couldn't manipulate the file presented to the PDF formatting process, that I would have to look within the Scribus file itself.
I chose the Baskerville (TrueType) within the text window option box itself and had no idea about either .ttc or .ttf. I've tried to see if the text box gives me the option to add the extension .ttf and it doesn't seem to let me. Given that Baskerville is one of the oldest type faces in existence, what can be done to add the magic .ttf to my file?
In exploring my Adobe conspiracy theory earlier, I had experimented exporting my file in PDF 1.3 and PDF 1.5 and the Baskerville sails through just fine. I copied my .sla file over to another Mac and exported to a PDF-x-1a which still had the old Adobe Reader (red logo). Voila, the Baskerville sailed through just fine, no Arial. Ah-ha Adobe! Upon closing and then opening a second time, that PDF-x-1a, the Arial had re-inserted itself. The Arial insertion is confined to the PDF/X exports only.
Something that might help is that the PDF/X export, as opposed to other PDF exports, also markedly alters the embedded background and text colors, indeed creating two different shades of text color depending on font size. In other words, inherent only to the PDF/X formats.
I have learned that part of this has to do with finely color "calibrating" my screen display to actually show the CMYK colors I'm choosing, however all the other exports show only a minor and consistent difference from my Scribus file while the PDF-x-1a shift is quite distorted.
Could the Baskerville-drop be related to the radical color shifts also occurring only in the PDF/X's?
Just in case you might want to examine this aspect I've attached both the CMYK icm and the RGB icm. I have no idea why the RGB portion is even there, since all the colors are CMYK chosen from within the Properties CMYK color palettes.