I am trying to use Scribus to format a manuscript for IngramSpark (if anyone has heard of them or, better yet, worked with them). IS requires PDF/X-1a:2001 or PDF/X-3:2002.
Resolution:600 ppi for 1-bit black & white line art
300 ppi for 8-bit grayscale continuous tone images
Color Space:Grayscale
LPI (lines per inch):106
Preferred file format:PDF (.pdf) file - dimensions vary by trim size (see below)
Bleed:0.125" (3 mm) except on bind side
PDF producer:Acrobat Distiller, Export from InDesign
PDF/X-1a:2001 or PDF/X-3:2002
Margins:Recommended minimum 0.5" (13 mm) on all sides.
File naming:Single file naming: isbn_txt.pdf or isbntxt.pdf
My problem is that the Scribus Preflight says everything checks out for both. But Adobe says there are no embedded fonts, and IS says it is unable to be validated. When I contacted support:
Listed below is the response from our IT department.
'The issue is that they converted all the text to paths. This is causing a problem with the preflight and would definitely not print. Please have them resolve and try again.
I don't know how I did this or what happened, but this is very frustrating, and I've been fighting with it for weeks trying to get it compliant. When I export it as a PDF, it has all the fonts embedded (figured out to disable the "subsets" in doc setup and pref). But Adobe says there are no embedded fonts.
On top of that, they require the interior to be grayscale, but I don't know if it's a problem yet because they say they can't even validate the file.
I really don't want to have to pay for Adobe when Scribus boasts compliant PDF/X. Help.

Edit: If it matters, the cover file has the same reqs, but CMYK instead of grayscale. It is image-only (no text frames) and it was accepted fine.
Edit Edit:
OS: Windows 10 64-bit
Scribus: 1.4.6 (tried downloading 1.5.3, but file crashed the program)