DyrckL

That's useful to know, thanks.

It seems that so long as you have a PDF-X profile selected the export works flawlessly.

I am a pre-press professional! And have been involved with colour management for many years. I both receive files for printing and send files out to other printers. I'm pretty sure that output intent is part of the PDF-X specification. In my comment above I had set everything to FOGRA39 (including within Acrobat) but was still seeing a 4 colour black on export. However, it is entirely possible that human error was part of the problem 🙂 I had expected setting PDF-X compatibility would include output intent. Over the years I have got used to asking customers to select PDF-X, usually 1a 2001, as their output profile and, with very few exceptions, this works. I am evaluating Affinity's products with a view to ditching Adobe's, I find Adobe's attitude to their customers high handed and essentially focussed on what is good for Adobe. They are dropping support for type 1 fonts in the future and if I am going to have to amend the thousands of documents that I have that include type 1 fonts I might as well take the opportunity to rebuild the files in one of Affinity's apps. Part of this process is to ensure that output PDFs behave themselves.

@Lagarto I had missed the fact that the PDF was missing an output intent. @Dan C any chance Affinity will get round to fixing this? It could well lead to issues when sending files to commercial printers.

Just to add a little to this conversation. I had a document with an object filled 0C, 0M, 0Y, 100K. It was CMYK/FOGRA39 in document setup and the PDF export was set to the same. When exported the PDF had a rich 4 colour black. I tried this a few times, using assign, convert, with profile embedded and without. I also tried starting with an RGB document and converting it and also starting with CMYK. After many attempts it worked and gave me the 100% black I needed. Unfortunately I can't quite give you the series of events that led to it working. It now works on all documents. On a related subject when an RGB black 0,0,0 is converted to CMYK/FOGRA39 it gives the same rich black 89, 69, 72, 97 colour split as the above conversion. It would be better if it gave a 100K black I think, there is very little use for that rich black.