Robert J A

Want to say a massive thank you to lacerto and thomaso – the printers have confirmed the files are now working. Hopefully the book will be ready in January!

THANK YOU ❤️

Want to say a massive thank you to lacerto and thomaso – the printers have confirmed the files are now working. Hopefully the book will be ready in January!

THANK YOU ❤️

Want to say a massive thank you to lacerto and thomaso – the printers have confirmed the files are now working. Hopefully the book will be ready in January!

THANK YOU ❤️

Thank you! I had setup the file similar to what you had suggested, however had not selected 1.4! Hopefully this sorts the problem.

Thank you all for taking the time to reply! Much appreciated.

Not "1.4" – The printer's screenshot & Lacerto said "X-4". (while PDF/X is required to force the Output Intent, requested in the printer's text)
printer:

PDF versions in Affinity:

It might be that what the printer wants is to have a DeviceCMYK print file with explicit color intent. The fact that the job seems to be based on PDF/X-4 standard additionally suggests, that possible live transparencies are wanted to be retained.
To have a similar output using Affinity Publisher, you would first need to ensure that you have the document CMYK profile set to one suggested by the printer. So for coated paper, PSO Coated v3 and for uncoated paper, PSO Uncoated v3. If you need to change the profile, use File > Document Setup > Color, and either the Convert option (if your current definitions are for clearly different media), and then ensure that you have text that you intend to print in mere black ink changed back to K-only (as they would be four-color black after conversion); or, use Assign method to keep all current color values.
After you have the correct CMYK document color profile, use the following export settings:

a) Compatibility PDF/X-4 forces use of color intent (which the printer obviously wants). It also retains all live transparencies of the document.
b) Color Space As document, keeps the PDF color space as CMYK (meaning that all native shapes no matter whether defined in RGB or CMYK will be converted to CMYK). PDF/X-4 does not require this, but as the printer instructed this, it is obvious that they want to have CMYK output.
c) ICC profile: Use document profile means that the PDF target profile will be the same as the document has: e.g. PSO Coated v3. In InDesign, you can change the color profile at this stage without causing conversion of CMYK color definitions, but in Affinity apps you cannot, so therefore you need to ensure that your document CMYK color profile is the same as that of the exported PDF.
d) Embed ICC profiles. This is a setting which you cannot change, but it will be irrelevant, because you are going to convert everything to target CMYK, that is, make a DeviceCMYK PDF, which is no longer ICC dependent and does not need to have profiles embedded. So there will be none included.
e) Convert image color spaces: checked. This converts the placed images to target CMYK, and leaves no alternate color spaces in the document. 
So, you will essentially produce a Device-CMYK document that has no ICC profiles embedded (because none are needed), but the correct target CMYK color profile intent declared explicitly (for whatever reason). You can tell this by using preflight apps like Adobe Acrobat Pro:

Why the printer wants specifically this kind of file, is not obvious, but as far as their InDesign-based specs are correctly given, the instructions shown above will produce what the printer expects.

Looking back at the file, at the time of posting it was definitely misbehaving, however checking again – looks like I must have resized the text box incorrectly. Going to keep an eye out to see if it happens again. I'm certain I wasn't resizing the new text box though and it was doing it.

Loved reading this thread! If we could get Affinity products on Linux.... That's BYE BYE Adobe, BYE BYE Windows! (Or Mac). All about variety of choice, and not monopoly.

Loved reading this thread! If we could get Affinity products on Linux.... That's BYE BYE Adobe, BYE BYE Windows! (Or Mac). All about variety of choice, and not monopoly.

Loved reading this thread! If we could get Affinity products on Linux.... That's BYE BYE Adobe, BYE BYE Windows! (Or Mac). All about variety of choice, and not monopoly.

Loved reading this thread! If we could get Affinity products on Linux.... That's BYE BYE Adobe, BYE BYE Windows! (Or Mac). All about variety of choice, and not monopoly.

Hi Tau Myx,
Welcome to Affinity Forums
No, all "lines" (segments) that conform a shape must have the same attributes (width, color etc). If you need to change the attributes of one segment you have to break the shape at the nodes that surround the segment you want using the Node Tool, selecting the nodes and clicking the Break Curve button in the Action section in the context toolbar (it's the first icon). You should now be able to select just that segment with the Move Tool and change its attributes.
No, you can't bend the unclosed line of an open shape. It's always a straight "line" connecting the start and end points.

Column guides are available in the most recent beta release.  They are set up from within Guides Manager.